SNLS491B July   2014  – February 2015 DS125BR820

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Electrical Characteristics — Serial Bus Interface DC Specifications
    7. 6.7 Serial Bus Interface Timing Specifications
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
      1. 7.2.1 Functional Datapath Blocks
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Pin Control Mode:
      2. 7.4.2 Slave SMBus Mode:
      3. 7.4.3 SMBus Master Mode
    5. 7.5 Signal Conditioning Settings
    6. 7.6 Programming
      1. 7.6.1 EEPROM Register Map for Single Device
    7. 7.7 Register Maps
      1. 7.7.1 Transfer Of Data Via The SMBus
      2. 7.7.2 SMBus Transactions
      3. 7.7.3 Writing a Register
      4. 7.7.4 Reading a Register
      5. 7.7.5 Detailed Register Map
  8. 8 Applications and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Signal Integrity in 40G-CR4/KR4/SAS/SATA/PCIe Applications
      2. 8.1.2 Signal Integrity in 40G-SR4/LR4 Applications
      3. 8.1.3 Rx Detect Functionality in 40G-CR4/KR4/SAS/SATA Applications
    2. 8.2 Typical Applications
      1. 8.2.1 Generic High Speed Repeater
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Performance Plots
      2. 8.2.2 Front Port Applications (40G-CR4/SR4/LR4)
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Performance Plots
      3. 8.2.3 PCIe Board Applications (PCIe Gen-3)
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Design Procedure
        3. 8.2.3.3 Application Performance Plots
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Trademarks
    2. 11.2 Electrostatic Discharge Caution
    3. 11.3 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7 Detailed Description

7.1 Overview

The DS125BR820 provides linear equalization for lossy printed circuit board backplanes and balanced cables. The DS125BR820 operates in three modes: Pin Control Mode (ENSMB = 0), SMBus Slave Mode (ENSMB = 1) and SMBus Master Mode (ENSMB = Float) to load register information from external EEPROM.

7.2 Functional Block Diagram

functional_block_diagram_wTerm.gif

7.2.1 Functional Datapath Blocks

In an increasing number of high speed applications, transparency between Tx and Rx endpoints is essential to ensure high signal integrity. The DS125BR820 channel datapath uses one input gain stage equalization coupled with a linear driver. This combination provides a high level of transparency, thereby achieving greater drive distance in applications such as 40G-CR4, 40G-KR4, SAS, SATA, and PCIe that require Rx-Tx auto-negotiation and link-training. Refer to the Typical Applications section for more application information regarding recommended settings and placement.

7.3 Feature Description

The 4-level input pins use a resistor divider to help set the four valid control levels and provide a wider range of control settings when ENSMB = 0. There is an internal 30 kΩ pull-up and a 60 kΩ pull-down connected to the package pin. These resistors, together with the external resistor connection, combine to achieve the desired voltage level. By using the 1 kΩ pull-down, 20 kΩ pull-down, no connect, and 1 kΩ pull-up, the optimal voltage levels for each of the four input states are achieved as shown in Table 1.

Table 1. 4–Level Control Pin Settings

RESULTING PIN VOLTAGE
LEVEL SETTING 3.3 V MODE 2.5 V MODE
0 Tie 1 kΩ to GND 0.10 V 0.08 V
R Tie 20 kΩ to GND 1/3 x VIN 1/3 x VDD
F Float (leave pin open) 2/3 x VIN 2/3 x VDD
1 Tie 1 kΩ to VIN or VDD VIN - 0.05 V VDD - 0.04 V

Typical 4-Level Input Thresholds

  • Internal Threshold between 0 and R = 0.2 * VIN or VDD
  • Internal Threshold between R and F = 0.5 * VIN or VDD
  • Internal Threshold between F and 1 = 0.8 * VIN or VDD

In order to minimize the startup current associated with the integrated 2.5 V regulator, the 1 kΩ pull-up / pull-down resistors are recommended. If several four level inputs require the same setting, it is possible to combine two or more 1 kΩ resistors into a single lower value resistor. As an example, combining two inputs with a single 500 Ω resistor is a valid way to save board space.

7.4 Device Functional Modes

7.4.1 Pin Control Mode:

When in Pin Mode (ENSMB = 0), equalization and VOD (output amplitude) can be selected via pin control for both the A-channels and B-channels per Table 4. The RXDET pin provides either automatic or manual control for input termination (50 Ω or > 50 kΩ to VDD). The receiver electrical signal detect status threshold is adjustable via the SD_TH pin. By setting signal-detect threshold level via the SD_TH pin, status information about a valid signal detect assert/de-assert can be read back via SMBus registers. Pin control mode is ideal in situations where neither MCU or EEPROM is available to access the device via SMBus SDA/SCL lines.

7.4.2 Slave SMBus Mode:

When in Slave SMBus Mode (ENSMB = 1), the VOD (output amplitude), equalization, and termination disable features are all programmable on an individual channel basis, rather than in collective A-channel and B-channel groups. Upon assertion of ENSMB, the EQx and VODx settings are controlled by SMBus immediately. It is important to note that SMBus settings can only be changed from their defaults after asserting Register Enable by setting Reg 0x06[3] = 1. The EQx and VODx pins are subsequently converted to AD0-AD3 SMBus address inputs. The other external control pins (RXDET and SD_TH) remain active unless their respective registers are written to and the appropriate override bit is set. If the user overrides a pin control, the input voltage level of that control pin is ignored until ENSMB is driven low (Pin Mode). In the event that channels are powered down via the PWDN pin, the state of all register settings are not affected.

Table 2. Rx Detect Settings

PWDN(1)
(Pin 52)		 RXDET
(Pin 22)		 SMBus REG
Bit[3:2]		 INPUT TERMINATION RECOMMENDED USE COMMENTS
0 0 00 Hi-Z Manual Rx-Detect, input is Hi-Z
0 R 01 Pre Detect: Hi-Z
Post Detect: 50 Ω		 PCIe Only Auto Rx-Detect, outputs test every 12 ms for 600 ms then stops; termination is Hi-Z until Rx detection; once detected input termination is 50 Ω
Reset function by pulsing PWDN high for 5 µs then low again
0 F
(Default)		 10 Pre Detect: Hi-Z
Post Detect: 50 Ω		 PCIe Only Auto Rx-Detect, outputs test every 12 ms until detection occurs; termination is Hi-Z until Rx detection; once detected input termination is 50 Ω
0 1 11 50 Ω 40G-CR4/SR4/LR4
SAS/SATA		 Manual Rx-Detect, input is 50 Ω
For 40G-CR4/SR4/LR4/SAS/SATA applications, it is required to use this setting.
1 X X Hi-Z Power Down mode, input is Hi-Z, output drivers are disabled

Used to reset Rx-Detect State Machine when held high for 5 µs
(1) In SMBus Slave Mode, the Rx Detect State Machine can be manually reset in software by overriding the device PRSNT function. This is accomplished by setting the Override PRSNT bit (Reg 0x02[7]) and then toggling the PRSNT value bit (Reg 0x02[6]). See Table 9 for more information about resetting the Rx Detect State Machine.

Table 3. Signal Detect Status Threshold Level(1)(2)

LEVEL SD_TH
(Pin 26)		 SMBus REG BIT[3:2] and[1:0] [3:2] ASSERT LEVEL (mVp-p) [1:0] DE-ASSERT LEVEL (mVp-p)
3 Gbps 12 Gbps 3 Gbps 12 Gbps
1 0 10 18 75 14 55
2 R 01 12 40 8 22
3 F (default) 00 15 50 11 37
4 1 11 16 58 12 45
(1) VDD = 2.5 V, 25°C, 11 00 11 00 pattern at 3 Gbps and 101010 pattern at 12 Gbps
(2) Signal detect status threshold sets the value at which a signal detect status is flagged via SMBus Reg 0x0A. Regardless of the threshold level, the output always remains enabled unless manually powered down.

7.4.3 SMBus Master Mode

When in SMBus Master Mode (ENSMB = Float), the VOD (output amplitude), equalization, and termination disable features for multiple devices can be loaded via external EEPROM. By asserting a Float condition on the ENSMB pin, an external EEPROM writes register settings to each device in accordance with its SMBus slave address. The settings programmable by external EEPROM provide only a subset of all the register bits available via SMBus Slave Mode, and the bit-mapping between SMBus Slave Mode registers and Master SMBus registers can be referenced in Table 6. Once the EEPROM successfully finishes loading each device's register settings, the device reverts back to SMBus Slave Mode and releases SDA/SCL control to an external master MCU. If the EEPROM fails to load settings to a particular device, for example due to an invalid or blank hex file, a time-out occurs and the device hangs in an unknown state.

7.5 Signal Conditioning Settings

Equalization and VOD settings accessible via the pin controls are chosen to meet the needs of most high speed applications. These settings can also be controlled via the SMBus registers. Each pin input has a total of four possible voltage level settings. Table 4 and Table 5 show both the Pin Mode and SMBus Mode settings that are used in order to program the equalization and VOD gain for each DS125BR820 channel.

Table 4. Equalizer Settings(1)(2)

EQUALIZATION BOOST RELATIVE to DC
LEVEL EQA(3)
EQB		 EQ – 8 bits[7:0] dB at
1.5 GHz		 dB at
2.5 GHz		 dB at
4 GHz		 dB at
5 GHz		 dB at
6 GHz
1 0 xxxx xx00 = 0x00 2.1 2.5 2.7 2.9 3.0
2 R xxxx xx01 = 0x01 4.0 5.1 6.4 6.8 7.4
3 F xxxx xx10 = 0x02 5.5 7.0 8.3 8.6 8.9
4 1 xxxx xx11 = 0x03 6.8 8.3 9.5 9.6 9.8
(1) Optimal EQ setting should be determined via simulation and prototype verification.
(2) Equalization boost values are inclusive of package loss.
(3) To program EQ Level 1-4 correctly in Pin Mode, RESERVED3 and AD2 pins must be tied via 1 kΩ resistor to GND.

Table 5. Output Voltage Settings(1)

LEVEL VODA1
VODB1		 VODA0
VODB0		 VOD - 3 bits[2:0] VOD_DB - 3 bits[2:0] VID Vp-p VOD/VID Ratio(1)
-- -- -- 000'b 000'b 1.2 0.57(2)
1 0 0 001'b 000'b 1.2 0.65
2 0 R 010'b 000'b 1.2 0.71
3 0 1 011'b 000'b 1.2 0.77
4 R F 100'b 000'b 1.2 0.83
5 F R 101'b 000'b 1.2 0.90
6 1 0 110'b 000'b 1.2 1.00
-- -- -- 111'b 000'b 1.2 1.04(2)(3)
(1) For 40G-CR4/KR4/SAS/SATA/PCIe operation, it is important to keep the output amplitude and dynamic range as large as possible. When operating in Pin Mode, it is recommended to use VODA[1:0] = VODB[1:0] = Level 6. In SMBus Mode, it is also recommended to use Level 6 (that is, VOD = 110'b and VOD_DB = 000'b).
(2) These VOD settings are only accessible via SMBus Modes.
(3) VOD = 111'b setting in SMBus Mode is not recommended.

7.6 Programming

The DS125BR820 device supports reading directly from an external EEPROM device by implementing SMBus Master Mode. When using SMBus Master Mode, the DS125BR820 reads directly from specific location in the external EEPROM. When designing a system for using the external EEPROM, the user must follow these specific guidelines.

  • Maximum EEPROM size is 8K (1024 x 8-bit).
  • Set ENSMB = Float — enable the SMBus Master Mode.
  • The external EEPROM device address byte must be 0xA0 and capable of 1 MHz operation at 2.5 V and 3.3 V supply.
  • Set the AD[3:0] inputs for SMBus address byte. When the AD[3:0] = 0000'b, the device address byte is 0xB0.

When tying multiple DS125BR820 devices to the SDA and SCL bus, use these guidelines to configure the devices:

  • Use SMBus AD[3:0] address bits so that each device can load its configuration from the EEPROM. Example below is for four devices. The first device in the sequence is conventionally address 0xB0, while subsequent devices follow the address order listed below.
    • U1: AD[3:0] = 0000 = 0xB0,
    • U2: AD[3:0] = 0001 = 0xB2,
    • U3: AD[3:0] = 0010 = 0xB4,
    • U4: AD[3:0] = 0011 = 0xB6
  • Use a pull-up resistor on SDA and SCL; value = 2 kΩ to 5 kΩ
  • Daisy-chain READ_EN (Pin 26) and ALL_DONE (Pin 27) from one device to the next device in the sequence so that they do not compete for the EEPROM at the same time.
    1. Tie READ_EN of the first device in the chain (U1) to GND.
    2. Tie ALL_DONE of U1 to READ_EN of U2.
    3. Tie ALL_DONE of U2 to READ_EN of U3.
    4. Tie ALL_DONE of U3 to READ_EN of U4.
    5. Optional: Tie ALL_DONE output of U4 to a LED to show the devices have been loaded successfully.

Once the ALL_DONE status pin of the last device is flagged to indicate that all devices sharing the SMBus line have been successfully programmed, control of the SMBus line is released by the repeater and the device reverts back to SMBus Slave Mode. At this point, an external MCU can perform any additional Read or Write operations.

Below is an example of a 2 kbits (256 x 8-bit) EEPROM in hex format for the DS125BR820 device. The first three bytes of the EEPROM always contain a base header common and necessary to control initialization of all devices connected to the I2C bus. The CRC enable flag is used to enable or disable CRC checking. If CRC checking is disabled, a fixed pattern (8’hA5) is written/read instead of the CRC byte from the CRC location to simplify the control. There is a MAP bit to flag the presence of an address map that specifies the configuration data start address in the EEPROM. If the MAP bit is not present, the configuration data start address is assumed to follow the base header directly. Lastly, one bit in the base header is used to indicate whether EEPROM size > 256 bytes. This bit ensures that EEPROM slot addresses are formatted properly as one byte (EEPROM ≤ 256 bytes) or two bytes (EEPROM > 256 bytes) for subsequent address map headers. There are 37 bytes of data for each DS125BR820 device.

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

Note: The maximum EEPROM size supported is 8 kbits (1024 x 8 bits).

7.6.1 EEPROM Register Map for Single Device

A detailed EEPROM Register Map for a single device is shown in Table 6. For instances where multiple devices are written to EEPROM, the device starting address definitions align starting with Table 6 Byte 0x03.

Table 6. EEPROM Register Map - Single Device With Default Value

EEPROM Address Byte Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Description 0x00 CRC_EN Address Map Present EEPROM > 256 Bytes Reserved DEVICE COUNT[3] DEVICE COUNT[2] DEVICE COUNT[1] DEVICE COUNT[0]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x01 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x02 Max EEPROM Burst size[7] Max EEPROM Burst size[6] Max EEPROM Burst size[5] Max EEPROM Burst size[4] Max EEPROM Burst size[3] Max EEPROM Burst size[2] Max EEPROM Burst size[1] Max EEPROM Burst size[0]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x03 PWDN_CH7 PWDN_CH6 PWDN_CH5 PWDN_CH4 PWDN_CH3 PWDN_CH2 PWDN_CH1 PWDN_CH0
SMBus Register 0x01[7] 0x01[6] 0x01[5] 0x01[4] 0x01[3] 0x01[2] 0x01[1] 0x01[0]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x04 Reserved Reserved Reserved Reserved Ovrd_PWDN Reserved Reserved Reserved
SMBus Register 0x02[5] 0x02[4] 0x02[3] 0x02[2] 0x02[0] 0x04[7] 0x04[6] 0x04[5]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x05 Reserved Reserved Reserved Reserved Reserved Reserved Ovrd_SD_TH Reserved
SMBus Register 0x04[4] 0x04[3] 0x04[2] 0x04[1] 0x04[0] 0x06[4] 0x08[6] 0x08[5]
Default Value 0x04 0 0 0 0 0 1 0 0
Description 0x06 Reserved Ovrd_RXDET Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x08[4] 0x08[3] 0x08[2] 0x08[1] 0x08[0] 0x0B[6] 0x0B[5] 0x0B[4]
Default Value 0x07 0 0 0 0 0 1 1 1
Description 0x07 Reserved Reserved Reserved Reserved Reserved Reserved CH0_RXDET_1 CH0_RXDET_0
SMBus Register 0x0B[3] 0x0B[2] 0x0B[1] 0x0B[0] 0x0E[5] 0x0E[4] 0x0E[3] 0x0E[2]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x08 Reserved Reserved Reserved Reserved Reserved Reserved CH0_EQ_1 CH0_EQ_0
SMBus Register 0x0F[7] 0x0F[6] 0x0F[5] 0x0F[4] 0x0F[3] 0x0F[2] 0x0F[1] 0x0F[0]
Default Value 0x2F 0 0 1 0 1 1 1 1
Description 0x09 CH0_SCP Reserved Reserved Reserved Reserved CH0_VOD_2 CH0_VOD_1 CH0_VOD_0
SMBus Register 0x10[7] 0x10[6] 0x10[5] 0x10[4] 0x10[3] 0x10[2] 0x10[1] 0x10[0]
Default Value 0xAD 1 0 1 0 1 1 0 1
Description 0x0A CH0_VOD_DB_2 CH0_VOD_DB_1 CH0_VOD_DB_0 Reserved CH0_THa_1 CH0_THa_0 CH0_THd_1 CH0_THd_0
SMBus Register 0x11[2] 0x11[1] 0x11[0] 0x12[7] 0x12[3] 0x12[2] 0x12[1] 0x12[0]
Default Value 0x40 0 1 0 0 0 0 0 0
Description 0x0B Reserved Reserved CH1_RXDET_1 CH1_RXDET_0 Reserved Reserved Reserved Reserved
SMBus Register 0x15[5] 0x15[4] 0x15[3] 0x15[2] 0x16[7] 0x16[6] 0x16[5] 0x16[4]
Default Value 0x02 0 0 0 0 0 0 1 0
Description 0x0C Reserved Reserved CH1_EQ_1 CH1_EQ_0 CH1_SCP Reserved Reserved Reserved
SMBus Register 0x16[3] 0x16[2] 0x16[1] 0x16[0] 0x17[7] 0x17[6] 0x17[5] 0x17[4]
Default Value 0xFA 1 1 1 1 1 0 1 0
Description 0x0D Reserved CH1_VOD_2 CH1_VOD_1 CH1_VOD_0 CH1_VOD_DB_2 CH1_VOD_DB_1 CH1_VOD_DB_0 Reserved
SMBus Register 0x17[3] 0x17[2] 0x17[1] 0x17[0] 0x18[2] 0x18[1] 0x18[0] 0x19[7]
Default Value 0xD4 1 1 0 1 0 1 0 0
Description 0x0E CH1_THa_1 CH1_THa_0 CH1_THd_1 CH1_THd_0 Reserved Reserved CH2_RXDET_1 CH2_RXDET_0
SMBus Register 0x19[3] 0x19[2] 0x19[1] 0x19[0] 0x1C[5] 0x1C[4] 0x1C[3] 0x1C[2]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x0F Reserved Reserved Reserved Reserved Reserved Reserved CH2_EQ_1 CH2_EQ_0
SMBus Register 0x1D[7] 0x1D[6] 0x1D[5] 0x1D[4] 0x1D[3] 0x1D[2] 0x1D[1] 0x1D[0]
Default Value 0x2F 0 0 1 0 1 1 1 1
Description 0x10 CH2_SCP Reserved Reserved Reserved Reserved CH2_VOD_2 CH2_VOD_1 CH2_VOD_0
SMBus Register 0x1E[7] 0x1E[6] 0x1E[5] 0x1E[4] 0x1E[3] 0x1E[2] 0x1E[1] 0x1E[0]
Default Value 0xAD 1 0 1 0 1 1 0 1
Description 0x11 CH2_VOD_DB_2 CH2_VOD_DB_1 CH2_VOD_DB_0 Reserved CH2_THa_1 CH2_THa_0 CH2_THd_1 CH2_THd_0
SMBus Register 0x1F[2] 0x1F[1] 0x1F[0] 0x20[7] 0x20[3] 0x20[2] 0x20[1] 0x20[0]
Default Value 0x40 0 1 0 0 0 0 0 0
Description 0x12 Reserved Reserved CH3_RXDET_1 CH3_RXDET_0 Reserved Reserved Reserved Reserved
SMBus Register 0x23[5] 0x23[4] 0x23[3] 0x23[2] 0x24[7] 0x24[6] 0x24[5] 0x24[4]
Default Value 0x02 0 0 0 0 0 0 1 0
Description 0x13 Reserved Reserved CH3_EQ_1 CH3_EQ_0 CH3_SCP Reserved Reserved Reserved
SMBus Register 0x24[3] 0x24[2] 0x24[1] 0x24[0] 0x25[7] 0x25[6] 0x25[5] 0x25[4]
Default Value 0xFA 1 1 1 1 1 0 1 0
Description 0x14 Reserved CH3_VOD_2 CH3_VOD_1 CH3_VOD_0 CH3_VOD_DB_2 CH3_VOD_DB_1 CH3_VOD_DB_0 Reserved
SMBus Register 0x25[3] 0x25[2] 0x25[1] 0x25[0] 0x26[2] 0x26[1] 0x26[0] 0x27[7]
Default Value 0xD4 1 1 0 1 0 1 0 0
Description 0x15 CH3_THa_1 CH3_THa_0 CH3_THd_1 CH3_THd_0 Reserved hi_idle_SD CH0-3 hi_idle_SD CH4-7 fast_SD CH0-3
SMBus Register 0x27[3] 0x27[2] 0x27[1] 0x27[0] 0x28[6] 0x28[5] 0x28[4] 0x28[3]
Default Value 0x09 0 0 0 0 1 0 0 1
Description 0x16 fast_SD CH4-7 lo_gain_SD CH0-3 lo_gain_SD CH4-7 Reserved Reserved CH4_RXDET_1 CH4_RXDET_0 Reserved
SMBus Register 0x28[2] 0x28[1] 0x28[0] 0x2B[5] 0x2B[4] 0x2B[3] 0x2B[2] 0x2C[7]
Default Value 0x80 1 0 0 0 0 0 0 0
Description 0x17 Reserved Reserved Reserved Reserved Reserved CH4_EQ_1 CH4_EQ_0 CH4_SCP
SMBus Register 0x2C[6] 0x2C[5] 0x2C[4] 0x2C[3] 0x2C[2] 0x2C[1] 0x2C[0] 0x2D[7]
Default Value 0x5F 0 1 0 1 1 1 1 1
Description 0x18 Reserved Reserved Reserved Reserved CH4_VOD_2 CH4_VOD_1 CH4_VOD_0 CH4_VOD_DB_2
SMBus Register 0x2D[6] 0x2D[5] 0x2D[4] 0x2D[3] 0x2D[2] 0x2D[1] 0x2D[0] 0x2E[2]
Default Value 0x5A 0 1 0 1 1 0 1 0
Description 0x19 CH4_VOD_DB_1 CH4_VOD_DB_0 Reserved CH4_THa_1 CH4_THa_0 CH4_THd_1 CH4_THd_0 Reserved
SMBus Register 0x2E[1] 0x2E[0] 0x2F[7] 0x2F[3] 0x2F[2] 0x2F[1] 0x2F[0] 0x32[5]
Default Value 0x80 1 0 0 0 0 0 0 0
Description 0x1A Reserved CH5_RXDET_1 CH5_RXDET_0 Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x32[4] 0x32[3] 0x32[2] 0x33[7] 0x33[6] 0x33[5] 0x33[4] 0x33[3]
Default Value 0x05 0 0 0 0 0 1 0 1
Description 0x1B Reserved CH5_EQ_1 CH5_EQ_0 CH5_SCP Reserved Reserved Reserved Reserved
SMBus Register 0x33[2] 0x33[1] 0x33[0] 0x34[7] 0x34[6] 0x34[5] 0x34[4] 0x34[3]
Default Value 0xF5 1 1 1 1 0 1 0 1
Description 0x1C CH5_VOD_2 CH5_VOD_1 CH5_VOD_0 CH5_VOD_DB_2 CH5_VOD_DB_1 CH5_VOD_DB_0 Reserved CH5_THa_1
SMBus Register 0x34[2] 0x34[1] 0x34[0] 0x35[2] 0x35[1] 0x35[0] 0x36[7] 0x36[3]
Default Value 0xA8 1 0 1 0 1 0 0 0
Description 0x1D CH5_THa_0 CH5_THd_1 CH5_THd_0 Reserved Reserved CH6_RXDET_1 CH6_RXDET_0 Reserved
SMBus Register 0x36[2] 0x36[1] 0x36[0] 0x39[5] 0x39[4] 0x39[3] 0x39[2] 0x3A[7]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x1E Reserved Reserved Reserved Reserved Reserved CH6_EQ_1 CH6_EQ_0 CH6_SCP
SMBus Register 0x3A[6] 0x3A[5] 0x3A[4] 0x3A[3] 0x3A[2] 0x3A[1] 0x3A[0] 0x3B[7]
Default Value 0x5F 0 1 0 1 1 1 1 1
Description 0x1F Reserved Reserved Reserved Reserved CH6_VOD_2 CH6_VOD_1 CH6_VOD_0 CH6_VOD_DB_2
SMBus Register 0x3B[6] 0x3B[5] 0x3B[4] 0x3B[3] 0x3B[2] 0x3B[1] 0x3B[0] 0x3C[2]
Default Value 0x5A 0 1 0 1 1 0 1 0
Description 0x20 CH6_VOD_DB_1 CH6_VOD_DB_0 Reserved CH6_THa_1 CH6_THa_0 CH6_THd_1 CH6_THd_0 Reserved
SMBus Register 0x3C[1] 0x3C[0] 0x3D[7] 0x3D[3] 0x3D[2] 0x3D[1] 0x3D[0] 0x40[5]
Default Value 0x80 1 0 0 0 0 0 0 0
Description 0x21 Reserved CH7_RXDET_1 CH7_RXDET_0 Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x40[4] 0x40[3] 0x40[2] 0x41[7] 0x41[6] 0x41[5] 0x41[4] 0x41[3]
Default Value 0x05 0 0 0 0 0 1 0 1
Description 0x22 Reserved CH7_EQ_1 CH7_EQ_0 CH7_SCP Reserved Reserved Reserved Reserved
SMBus Register 0x41[2] 0x41[1] 0x41[0] 0x42[7] 0x42[6] 0x42[5] 0x42[4] 0x42[3]
Default Value 0xF5 1 1 1 1 0 1 0 1
Description 0x23 CH7_VOD_2 CH7_VOD_1 CH7_VOD_0 CH7_VOD_DB_2 CH7_VOD_DB_1 CH7_VOD_DB_0 Reserved CH7_THa_1
SMBus Register 0x42[2] 0x42[1] 0x42[0] 0x43[2] 0x43[1] 0x43[0] 0x44[7] 0x44[3]
Default Value 0xA8 1 0 1 0 1 0 0 0
Description 0x24 CH7_THa_0 CH7_THd_1 CH7_THd_0 Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x44[2] 0x44[1] 0x44[0] 0x47[3] 0x47[2] 0x47[1] 0x47[0] 0x48[7]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x25 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x48[6] 0x4C[7] 0x4C[6] 0x4C[5] 0x4C[4] 0x4C[3] 0x4C[0] 0x59[0]
Default Value 0x00 0 0 0 0 0 0 0 0
Description 0x26 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x5A[7] 0x5A[6] 0x5A[5] 0x5A[4] 0x5A[3] 0x5A[2] 0x5A[1] 0x5A[0]
Default Value 0x54 0 1 0 1 0 1 0 0
Description 0x27 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x5B[7] 0x5B[6] 0x5B[5] 0x5B[4] 0x5B[3] 0x5B[2] 0x5B[1] 0x5B[0]
Default Value 0x54 0 1 0 1 0 1 0 0

Table 7. Example Of EEPROM for Four Devices Using Two Address Maps

EEPROM
ADDRESS		 ADDRESS
(Hex)		 EEPROM
DATA		 COMMENTS
0 00 0x43 CRC_EN = 0, Address Map = 1, >256 bytes = 0, Device Count[3:0] = 3
1 01 0x00
2 02 0x10 EEPROM Burst Size
3 03 0x00 CRC not used
4 04 0x0B Device 0 Address Location
5 05 0x00 CRC not used
6 06 0x0B Device 1 Address Location
7 07 0x00 CRC not used
8 08 0x30 Device 2 Address Location
9 09 0x00 CRC not used
10 0A 0x30 Device 3 Address Location
11 0B 0x00 Begin Device 0, 1 - Address Offset 3
12 0C 0x00
13 0D 0x04
14 0E 0x07
15 0F 0x00
16 10 0x01 EQ CHB0 = 0x01
17 11 0xAD VOD CHB0 = 101'b
18 12 0x00 VOD_DB CHB0 = 000'b
19 13 0x00
20 14 0x1A EQ CHB1 = 0x01
21 15 0xD0 VOD CHB1 = 101'b, VOD_DB CHB1 = 000'b
22 16 0x00
23 17 0x01 EQ CHB2 = 0x01
24 18 0xAD VOD CHB2 = 101'b
25 19 0x00 VOD_DB CHB2 = 000'b
26 1A 0x00
27 1B 0x1A EQ CHB3 = 0x01
28 1C 0xD0 VOD CHB3 = 101'b, VOD_DB CHB3 = 000'b
29 1D 0x09 Signal Detect Status Threshold Control
30 1E 0x80 Signal Detect Status Threshold Control
31 1F 0x07 EQ CHA0 = 0x03
32 20 0x5C VOD CHA0 = 110'b
33 21 0x00 VOD_DB CHA0 = 000'b
34 22 0x00
35 23 0x15 EQ CHA1 = 0x00
36 24 0xC0 VOD CHA1 = 110'b, VOD_DB CHA1 = 000'b
37 25 0x00
38 26 0x07 EQ CHA2 = 0x03
39 27 0x5C VOD CHA2 = 110'b
40 28 0x00 VOD_DB CHA2 = 000'b
41 29 0x00
42 2A 0x75 EQ CHA3 = 0x00
43 2B 0xC0 VOD CHA3 = 110'b, VOD_DB CHA3 = 000'b
44 2C 0x00
45 2D 0x00
46 2E 0x54
47 2F 0x54 End Device 0, 1 - Address Offset 39
48 30 0x00 Begin Device 2, 3 - Address Offset 3
49 31 0x00
50 32 0x04
51 33 0x07
52 34 0x00
53 35 0x01 EQ CHB0 = 0x01
54 36 0xAB VOD CHB0 = 011'b
55 37 0x00 VOD_DB CHB0 = 000'b
56 38 0x00
57 39 0x1A EQ CHB1 = 0x01
58 3A 0xB0 VOD CHB1 = 011'b, VOD_DB CHB1 = 000'b
59 3B 0x00
60 3C 0x01 EQ CHB2 = 0x01
61 3D 0xAB VOD CHB2 = 011'b
62 3E 0x00 VOD_DB CHB2 = 000'b
63 3F 0x00
64 40 0x1A EQ CHB3 = 0x01
65 41 0xB0 VOD CHB3 = 011'b, VOD_DB CHB3 = 000'b
66 42 0x09 Signal Detect Status Threshold Control
67 43 0x80 Signal Detect Status Threshold Control
68 44 0x07 EQ CHA0 = 0x03
69 45 0x5C VOD CHA0 = 110'b
70 46 0x00 VOD_DB CHA0 = 000'b
71 47 0x00
72 48 0x15 EQ CHA1 = 0x00
73 49 0xA0 VOD CHA1 = 101'b, VOD_DB CHA1 = 000'b
74 4A 0x00
75 4B 0x07 EQ CHA2 = 0x03
76 4C 0x5C VOD CHA2 = 110'b
77 4D 0x00 VOD_DB CHA2 = 000'b
78 4E 0x00
79 4F 0x15 EQ CHA3 = 0x00
80 50 0xA0 VOD CHA3 = 101'b, VOD_DB CHA3 = 000'b
81 51 0x00
82 52 0x00
83 53 0x54
84 54 0x54 End Device 2, 3 - Address Offset 39

Note: CRC_EN = 0, Address Map = 1, >256 byte = 0, Device Count[3:0] = 3. Multiple devices can point to the same address map. Maximum EEPROM size is 8 kbits (1024 x 8-bits).

7.7 Register Maps

The System Management Bus interface is compatible to SMBus 2.0 physical layer specification. Tie ENSMB = 1 kΩ to VDD (2.5 V mode) or VIN (3.3 V mode) to enable SMBus Slave Mode and allow access to the configuration registers.

The DS125BR820 uses AD[3:0] inputs in both SMBus Modes. These AD[3:0] pins are the user set SMBus slave address inputs and have internal pull-downs. Based on the SMBus 2.0 specification, the DS125BR820 has a 7-bit slave address. The LSB is set to 0'b (for a WRITE). When AD[3:0] pins are left floating or pulled low, AD[3:0] = 0000'b, and the device default address byte is 0xB0. The device supports up to 16 address bytes, as shown in Table 8:

Table 8. Device Slave Address Bytes

AD[3:0] SETTINGS FULL SLAVE ADDRESS BYTE
(7-Bit ADDRESS + WRITE BIT)		 7-Bit SLAVE
ADDRESS (HEX)
0000 B0 58
0001 B2 59
0010 B4 5A
0011 B6 5B
0100 B8 5C
0101 BA 5D
0110 BC 5E
0111 BE 5F
1000 C0 60
1001 C2 61
1010 C4 62
1011 C6 63
1100 C8 64
1101 CA 65
1110 CC 66
1111 CE 67

The SDA/SCL pins are 3.3 V tolerant, but are not 5V tolerant. An external pull-up resistor is required on the SDA line. The resistor value can be from 2 kΩ to 5 kΩ depending on the voltage, loading and speed. The SCL may also require an external pull-up resistor and it depends on the Host that drives the bus.

7.7.1 Transfer Of Data Via The SMBus

During normal operation, the data on SDA must be stable during the time when SCL is High.

There are three unique states for the SMBus:

START: A High-to-Low transition on SDA while SCL is High indicates a message START condition.

STOP: A Low-to-High transition on SDA while SCL is High indicates a message STOP condition.

IDLE: If SCL and SDA are both High for a time exceeding tBUF from the last detected STOP condition or if they are High for a total exceeding the maximum specification for tHIGH, then the bus transfers to the IDLE state.

7.7.2 SMBus Transactions

The device supports WRITE and READ transactions. See Table 9 for register address, type (Read/Write, Read Only), default value, and function information.

7.7.3 Writing a Register

To write a register, the following protocol is used (see SMBus 2.0 specification).

  1. The Host drives a START condition, the 7-bit SMBus address, and a “0” indicating a WRITE.
  2. The Device (Slave) drives the ACK bit (“0”).
  3. The Host drives the 8-bit Register Address.
  4. The Device drives an ACK bit (“0”).
  5. The Host drive the 8-bit data byte.
  6. The Device drives an ACK bit (“0”).
  7. The Host drives a STOP condition.

The WRITE transaction is completed, the bus goes IDLE, and communication with other SMBus devices may now occur.

7.7.4 Reading a Register

To read a register, the following protocol is used (see SMBus 2.0 specification).

  1. The Host drives a START condition, the 7-bit SMBus address, and a “0” indicating a WRITE.
  2. The Device (Slave) drives the ACK bit (“0”).
  3. The Host drives the 8-bit Register Address.
  4. The Device drives an ACK bit (“0”).
  5. The Host drives a START condition.
  6. The Host drives the 7-bit SMBus Address, and a “1” indicating a READ.
  7. The Device drives an ACK bit “0”.
  8. The Device drives the 8-bit data value (register contents).
  9. The Host drives a NACK bit “1”indicating end of the READ transfer.
  10. The Host drives a STOP condition.

The READ transaction is completed, the bus goes IDLE, and communication with other SMBus devices may now occur.

7.7.5 Detailed Register Map

Table 9. SMBus Slave Mode Register Map

Address Register
Name		 Bit Field Type Default EEPROM
Reg Bit		 Description
0x00 Observation 7 Reserved R/W 0x00 Set bit to 0
6:3 Address Bit
AD[3:0]		 R Observation of AD[3:0] bits
[6]: AD3
[5]: AD2
[4]: AD1
[3]: AD0
2 EEPROM Read Done R 1 = Device completed the read from external EEPROM
1 Reserved R/W Set bit to 0
0 Reserved R/W Set bit to 0
0x01 PWDN Channels 7:0 PWDN CHx R/W 0x00 Yes Power Down per Channel
[7]: CH7 – CHA_3
[6]: CH6 – CHA_2
[5]: CH5 – CHA_1
[4]: CH4 – CHA_0
[3]: CH3 – CHB_3
[2]: CH2 – CHB_2
[1]: CH1 – CHB_1
[0]: CH0 – CHB_0
0x00 = all channels enabled
0xFF = all channels disabled
Note: Override PWDN pin and enable register control via Reg 0x02[0]
0x02 Override PWDN, PRSNT 7 Override PRSNT R/W 0x00 1 = Override Automatic Rx Detect State Machine Reset
6 PRSNT Value 1 = Set Rx Detect State Machine Reset
0 = Clear Rx Detect State Machine Reset
5:2 Reserved Yes Set bits to 0
1 Reserved Set bit to 0
0 Override PWDN Yes 1 = Block PWDN pin control (Register control enabled)
0 = Allow PWDN pin control (Register control disabled)
0x03 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x04 Reserved 7:0 Reserved R/W 0x00 Yes Set bits to 0
0x05 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x06 Slave Register Control 7:5 Reserved R/W 0x10 Set bits to 0
4 Reserved Yes Set bit to 1
3 Register Enable 1 = Enable SMBus Slave Mode Register Control
Note: In order to change VOD, VOD_DB, and EQ of the channels in slave mode, this bit must be set to 1.
2:0 Reserved Set bits to 0
0x07 Digital Reset and Control 7 Reserved R/W 0x01 Set bit to 0
6 Reset Registers 1 = Self clearing reset for SMBus registers (register settings return to default values)
5 Reset SMBus Master 1 = Self clearing reset to SMBus master state machine
4:0 Reserved Set bits to 0 0001'b
0x08 Override
Pin Control 		7 Reserved R/W 0x00 Set bit to 0
6 Override SD_TH Yes 1 = Block SD_TH pin control (Register control enabled)
0 = Allow SD_TH pin control (Register control disabled)
5:4 Reserved Yes Set bits to 0
3 Override RXDET Yes 1 = Block RXDET pin control (Register control enabled)
0 = Allow RXDET pin control (Register control disabled)
2:0 Reserved Yes Set bits to 0
0x09 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x0A Signal Detect Monitor 7:0 SD_TH Status R 0x00 CH7 - CH0 Internal Signal Detect Indicator
[7]: CH7 – CHA_3
[6]: CH6 – CHA_2
[5]: CH5 – CHA_1
[4]: CH4 – CHA_0
[3]: CH3 – CHB_3
[2]: CH2 – CHB_2
[1]: CH1 – CHB_1
[0]: CH0 – CHB_0
0 = Signal detected at input
1 = Signal not detected at input
Note: These bits only function when RESERVED2 pin = FLOAT
0x0B Reserved 7 Reserved R/W 0x00 Set bit to 0
6:0 Reserved R/W 0x70 Yes Set bits to 111 0000'b
0x0C-0x0D Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x0E CH0 - CHB_0
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x0F CH0 - CHB_0
EQ		 7:0 EQ Control R/W 0x2F Yes INB_0 EQ Control - total of four levels.
See Table 4.
0x10 CH0 - CHB_0
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTB_0 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x11 CH0 - CHB_0
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH0 - CHB_0
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTB_0 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x12 CH0 - CHB_0
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x13-0x14 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x15 CH1 - CHB_1
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x16 CH1 - CHB_1
EQ		 7:0 EQ Control R/W 0x2F Yes INB_1 EQ Control - total of four levels.
See Table 4.
0x17 CH1 - CHB_1
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTB_1 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x18 CH1 - CHB_1
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH1 - CHB_1
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTB_1 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x19 CH1 - CHB_1
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x1A-0x1B Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x1C CH2 - CHB_2
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x1D CH2 - CHB_2
EQ		 7:0 EQ Control R/W 0x2F Yes INB_2 EQ Control - total of four levels.
See Table 4.
0x1E CH2 - CHB_2
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTB_2 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x1F CH2 - CHB_2
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH2 - CHB_2
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTB_2 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x20 CH2 - CHB_2
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x21-0x22 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x23 CH3 - CHB_3
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x24 CH3 - CHB_3
EQ		 7:0 EQ Control R/W 0x2F Yes INB_3 EQ Control - total of four levels.
See Table 4.
0x25 CH3 - CHB_3
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTB_3 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x26 CH3 - CHB_3
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH3 - CHB_3
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTB_3 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x27 CH3 - CHB_3
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x28 Signal Detect Status Control 7 Reserved R/W 0x4C Set bit to 0
6 Reserved Yes Set bit to 1
5:4 High SD_TH Status Yes Enable Higher Range of Signal Detect Status Thresholds
[5]: CH0 - CH3
[4]: CH4 - CH7
3:2 Fast Signal Detect Status Yes Enable Fast Signal Detect Status
[3]: CH0 - CH3
[2]: CH4 - CH7
Note: In Fast Signal Detect, assert/de-assert response occurs after approximately 3-4 ns
1:0 Reduced SD Status Gain Yes Enable Reduced Signal Detect Status Gain
[1]: CH0 - CH3
[0]: CH4 - CH7
0x29-0x2A Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x2B CH4 - CHA_0
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x2C CH4 - CHA_0
EQ		 7:0 EQ Control R/W 0x2F Yes INA_0 EQ Control - total of four levels.
See Table 4.
0x2D CH4 - CHA_0
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTA_0 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x2E CH4 - CHA_0
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH4 - CHA_0
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTA_0 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x2F CH4 - CHA_0
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x30-0x31 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x32 CH5 - CHA_1
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x33 CH5 - CHA_1
EQ		 7:0 EQ Control R/W 0x2F Yes INA_1 EQ Control - total of four levels.
See Table 4.
0x34 CH5 - CHA_1
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTA_1 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x35 CH5 - CHA_1
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH5 - CHA1
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTA_1 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x36 CH5 - CHA_1
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x37-0x38 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x39 CH6 - CHA_2
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x3A CH6 - CHA_2
EQ		 7:0 EQ Control R/W 0x2F Yes INA_2 EQ Control - total of four levels.
See Table 4.
0x3B CH6 - CHA_2
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTA_2 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x3C CH6 - CHA_2
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH6 - CHA_2
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTA_2 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x3D CH6 - CHA_2
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x3E-0x3F Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x40 CH7 - CHA_3
RXDET		 7:6 Reserved R/W 0x00 Set bits to 0
5:4 Reserved Yes Set bits to 0
3:2 RXDET Yes 00'b = Input is Hi-Z impedance
01'b = Auto Rx-Detect,
outputs test every 12 ms for 600 ms (50 times) then stops; termination is Hi-Z until detection; once detected input termination is 50 Ω
10'b = Auto Rx-Detect,
outputs test every 12 ms until detection occurs; termination is Hi-Z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: Override RXDET pin and enable register control via Reg 0x08[3]
1:0 Reserved Set bits to 0
0x41 CH7 - CHA_3
EQ		 7:0 EQ Control R/W 0x2F Yes INA_3 EQ Control - total of four levels.
See Table 4.
0x42 CH7 - CHA_3
VOD 		7 Short Circuit Protection R/W 0xAD Yes 1 = Enable the short circuit protection
0 = Disable the short circuit protection
6:3 Reserved Yes Set bits to 0101'b
2:0 VOD Control Yes OUTA_3 VOD Control: VOD / VID Ratio
000'b = 0.57
001'b = 0.65
010'b = 0.71
011'b = 0.77
100'b = 0.83
101'b = 0.90 (default)
110'b = 1.00 (recommended)
111'b = 1.04
0x43 CH7 - CHA_3
VOD_DB		 7 RXDET Status R 0x02 Observation bit for RXDET CH7 - CHA_3
1 = Input 50 Ω terminated to VDD
0 = Input is Hi-Z
6:5 Reserved Set bits to 0
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control Yes OUTA_3 VOD_DB Control
000'b = 0 dB (recommended)
001'b = –1.5 dB
010'b = –3.5 dB (default)
011'b = –5 dB
100'b = –6 dB
101'b = –8 dB
110'b = –9 dB
111'b = –12 dB
Note: Changing VOD_DB bits effectively lowers the output VOD dynamic range by a factor of the corresponding amount of dB reduction.
0x44 CH7 - CHA_3
SD_TH		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status Assert Threshold Yes Status Assert threshold (1010 pattern 12 Gbps)
00'b = 50 mVp-p (default)
01'b = 40 mVp-p
10'b = 75 mVp-p
11'b = 58 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
1:0 Signal Detect Status
De-assert Threshold		 Yes Status De-assert threshold (1010 pattern 12 Gbps)
00'b = 37 mVp-p (default)
01'b = 22 mVp-p
10'b = 55 mVp-p
11'b = 45 mVp-p
Note: Override SD_TH pin and enable register control via Reg 0x08[6]
0x45 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x46 Reserved 7:0 Reserved R/W 0x38 Set bits to 0x38
0x47 Reserved 7:4 Reserved R/W 0x00 Set bits to 0
3:0 Reserved Yes Set bits to 0
0x48 Reserved 7:6 Reserved R/W 0x05 Yes Set bits to 0
5:0 Reserved R/W Set bits to 00 0101'b
0x49-0x4B Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x4C Reserved 7:3 Reserved R/W 0x00 Yes Set bits to 0
2:1 Reserved R/W Set bits to 0
0 Reserved R/W Yes Set bits to 0
0x4D-0x50 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x51 Device ID 7:5 VERSION R 0x85 100'b
4:0 ID 0 0101'b
0x52-0x55 Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x56 Reserved 7:0 Reserved R/W 0x10 Set bits to 0x10
0x57 Reserved 7:0 Reserved R/W 0x64 Set bits to 0x64
0x58 Reserved 7:0 Reserved R/W 0x21 Set bits to 0x21
0x59 Reserved 7:1 Reserved R/W 0x00 Set bits to 0
0 Reserved Yes Set bit to 0
0x5A Reserved 7:0 Reserved R/W 0x54 Yes Set bits to 0x54
0x5B Reserved 7:0 Reserved R/W 0x54 Yes Set bits to 0x54
0x5C-0x61 Reserved 7:0 Reserved R/W 0x00 Set bits to 0