SNLS430C October   2012  – August 2014 DS125BR111

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Electrical Characteristics — Serial Management Bus Interface
    7. 7.7 Timing Requirements
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
      1. 8.2.1 Functional Datapath Blocks
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
      1. 8.4.1 Pin Control Mode
      2. 8.4.2 SMBus Mode
      3. 8.4.3 Signal Conditioning Settings
    5. 8.5 Programming
    6. 8.6 Register Maps
      1. 8.6.1 Transfer Of Data Via The SMBus
      2. 8.6.2 SMBus Transactions
      3. 8.6.3 Writing a Register
      4. 8.6.4 Reading a Register
      5. 8.6.5 SMBus Register Information
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Signal Integrity
      2. 9.1.2 RX-Detect in SAS/SATA Applications
      3. 9.1.3 PCIe Applications
        1. 9.1.3.1 RXDET When Using SMBus Modes
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

8 Detailed Description

8.1 Overview

The DS125BR111 compensates for lossy FR-4 printed circuit board backplanes and balanced cables. The DS125BR111 operates in 3 modes: pin Control Mode (ENSMB = 0), SMBus Slave Mode (ENSMB = 1) and SMBus Master Mode (ENSMB = float) to load register information from external EEPROM; please refer to SMBus Master Mode for additional information.

8.2 Functional Block Diagram

111blk.gifFigure 8. Channel A/B Datapath

8.2.1 Functional Datapath Blocks

The DS125BR111 datapath is designed to provide transparency for Rx-Tx training in SAS-3, PCIe Gen3, and other standards. The datapath includes input continuous time linear equalization coupled with a linear driver. This combination has a high level of transparency, achieving greater drive distance in applications which utilize Rx-Tx training.

The DS125BR111 datapath is optimized to work as a transparent driver and a transparent receiver. The typical DS125BR111 system placement breaks a long transmission line into two pieces. This often leads to one short and one long piece. While the DS125BR111 can be placed anywhere in the channel, to maximize channel extension placement with some attenuation on the DS125BR111 inputs works best. Refer to Application and Implementation for more application information regarding device placement.

8.3 Feature Description

The 4-level input pins utilize a resistor divider to help set the 4 valid 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. Using the 1 kΩ pull-up, 1 kΩ pull-down, no connect, and 20 kΩ pull-down provide the optimal voltage levels for each of the four input states.

Table 1. 4–Level Control Pin Settings

LEVEL SETTING RESULTING PIN VOLTAGE
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
Float 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

  • Level 1 - 2 = 0.16 * VIN or VDD
  • Level 2 - 3 = 0.5 * VIN or VDD
  • Level 3 - 4 = 0.83 * 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 4 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 good way to save board space.

8.4 Device Functional Modes

8.4.1 Pin Control Mode

When in Pin mode (ENSMB = 0), equalization can be selected via pins for each side independently. For PCIe applications, the RXDET pin provides automatic and manual control for input termination (50 Ω or > 50 kΩ). The receiver electrical signal detect threshold is also adjustable via the SD_TH pin. The signal detect status can only be used for system debug.

8.4.2 SMBus Mode

When in SMBus mode (ENSMB = 1), the VOD (output amplitude), equalization, and termination disable features are all programmable on a individual channel basis. Upon assertion of ENSMB = 1, the EQx, VOD, and VODx_DB functions revert to register control immediately. The EQx pins are converted to AD0-AD3 SMBus address inputs. SD_TH remains active unless their respective registers are written to and the appropriate override bit is set, in which case it is ignored until ENSMB is driven low (Pin mode). On power-up or when ENSMB is driven low all registers are reset to their default state. If PWDN is asserted while ENSMB is high, the registers retain their current state.

Equalization settings accessible via the Pin controls were chosen to meet the needs of most high speed applications. If ongoing adjustment is needed, equalization settings can be accessed via the SMBus registers. Each input has a total of 4 possible equalization settings. The tables show the 4 settings when the device is in Pin mode. When using SMBus mode, the equalization, VOD and VOD_DB levels are set by registers.

The 4-level input Pins utilize a resistor divider to help set the 4 valid levels and provide a wide 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. Using the 1 kΩ pull-up, 1 kΩ pull-down, no connect, and 20 kΩ pull-down provide the optimal voltage levels for each of the four input states.

Table 2. RX-Detect Settings

PWDN
(Pin 6)		 RXDET
(Pin 18)		 SMBus REG
0x0E and 0X15[3:2]		 INPUT TERMINATION RECOMMENDED USE COMMENTS
0 0 00'b Hi-Z Manual RX-Detect, input is high impedance mode
0 Tie 20 kΩ
to GND		 01'b 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 Float
(PCIe Default)		 10'b 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
(SAS Default)		 11'b 50 Ω All Others Manual RX-Detect, input is 50 Ω
1 X High Impedance Power down mode, input is Hi-Z, output drivers are disabled

Used to reset RX-Detect State Machine when held high for 5 µsec

When SMBus is used to control the DS125BR111 in a PCIe application, a specific register write sequence detailed in PCIe Applications is required on power-up to properly enable and control the RX_Detect process.

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

SD_TH
(Pin 14)		 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
0 10 18 75 14 55
R 01 12 40 8 22
F (default) 00 15 50 11 37
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 Threshold (SD_TH) is for debugging purposes only, outputs are enabled unless the channel is set to PWDN

8.4.3 Signal Conditioning Settings

Table 4. Equalizer Settings

EQUALIZATION BOOST RELATIVE TO DC
Level EQx1 EQx0 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		 Suggested Use(1)
1 0 0 xxxx xx00 = 0x00 2.1 2.5 2.7 2.9 3.0
2 0 R xxxx xx01 = 0x01 4.0 5.1 6.4 6.8 7.4
3 0 Float xxxx xx10 = 0x02 5.5 7.0 8.3 8.6 8.9
4 0 1 xxxx xx11 = 0x03 6.8 8.3 9.5 9.6 9.8 SAS-3
(1) For SAS3 applications the best performance is achieved with Equalization Level 4. For non SAS applications, optimal EQ setting should be determined via simulation and prototype verification.

Table 5. Output Voltage Pin Settings

Channel A Level Channel B Level VOD_SEL VID Vp-p VODx_DB Setting(1) VOD Vp-p
0 0 1.0 0 0.65
1 0 1.0 0 0.70
3 3 R 1.0 0 0.83
5 5 Float 1.0 0 0.91
7 7 1 1.0 0 1.05
(1) The VOD output amplitude is set with the VOD_SEL Pin. For SAS-3 and PCIe operation the VOD_DB level is typically left at 0 dB (SMBus control = 000'b) in order to keep the output dynamic range as large as possible. VOD_DB settings other than 0 dB or 000'b will decrease the output dynamic range and act to limit the output VOD. When operating in Pin Mode in a SAS3 environment it is recommended to use VOD_SEL = 1.

8.5 Programming

The DS125BR111 device supports reading directly from an external EEPROM device by implementing SMBus Master mode. When using the SMBus master mode, the DS125BR111 will read directly from specific location in the external EEPROM. When designing a system for using the external EEPROM, the user needs to follow these specific guidelines.

  • Maximum EEPROM size is 8 kbits (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. The VOD_SEL/READEN pin must be tied Low for the AD[3:0] to be active. If this pin is tied High or Floated an address of 0xB0 will be used for the DS125BR111.

When tying multiple DS125BR111 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 loaded it's configuration from the EEPROM. Example below is for 4 devices. The first device in the sequence must be address 0xB0, subsequent devices must 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; typical value = 2 kΩ - 5 kΩ
  • Daisy-chain READEN (Pin 17) and DONE (Pin 18) 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 READEN of the 1st device in the chain (U1) to GND
    2. Tie DONE of U1 to READEN of U2
    3. Tie DONE of U2 to READEN of U3
    4. Tie DONE of U3 to READEN of U4
    5. Optional: Tie DONE output of U4 to a LED to show the devices have been loaded successfully

Below is an example using the default register values of a 2 kbit (256 x 8-bit) EEPROM in hex format for the DS125BR111 device. The first 3 bytes of the EEPROM always contain a header common and necessary to control initialization of all devices connected to the I2C bus. CRC enable flag to enable/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 in the EEPROM. If the MAP bit is not present the configuration data start address is derived from the DS125BR111 address and the configuration data size. A bit to indicate an EEPROM size > 256 bytes is necessary to properly address the EEPROM. There are 37 bytes of data size for each DS125BR111 device.

:2000000000001000000407002FED4002FED4002FAD4002FAD400005F5A8005F5A8005F5A15 :200020008005F5A800005454000000000000000000000000000000000000000000000000F6 :20006000000000000000000000000000000000000000000000000000000000000000000080 :20008000000000000000000000000000000000000000000000000000000000000000000060 :2000A000000000000000000000000000000000000000000000000000000000000000000040 :2000C000000000000000000000000000000000000000000000000000000000000000000020 :2000E000000000000000000000000000000000000000000000000000000000000000000000 :200040000000000000000000000000000000000000000000000000000000000000000000A0

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

Note: Default register values. These should be changed as indicated in the datasheet to support PCIe and SAS/SATA

Table 6. EEPROM Register Map - Single Device With SAS Values

EEPROM Address Byte Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 BIt 0
Description 0 CRC EN Address Map Present EEPROM > 256 Bytes RES DEVICE COUNT[3] DEVICE COUNT[2] DEVICE COUNT[1] DEVICE COUNT[0]
Value 00 0 0 0 0 0 0 0 0
Description 1 RES RES RES RES RES RES RES RES
Value 00 0 0 0 0 0 0 0 0
Description 2 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]
Value 00 0 0 0 0 0 0 0 0
Description 3 Reserved Reserved Reserved Reserved Reserved Reserved ENABLE_CHB ENABLE_CHA
SMBus Register 0x01 [7] 0x01 [6] 0x01 [5] 0x01 [4] 0x01 [3] 0x01 [2] 0x01 [1] 0x01 [0]
Value 00 0 0 0 0 0 0 0 0
Description 4 Reserved Reserved Reserved Reserved Ovrd_ENABLE Reserved Reserved Reserved
SMBus Register 0x02 [5] 0x02 [4] 0x02 [3] 0x02 [2] 0x02 [0] 0x04 [7] 0x04 [6] 0x04 [5]
Value 00 0 0 0 0 0 0 0 0
Description 5 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]
Value 04 0 0 0 0 0 1 0 0
Description 6 Reserved Ovrd_RX_Detect Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x08 [4] 0x08 [3] 0x08 [2] 0x08 [1] 0x08 [0] 0x0B [6] 0x0B [5] 0x0B [4]
Value 07 0 0 0 0 0 1 1 1
Description 7 rate_delay_3 rate_delay_2 rate_delay_1 rate_delay_0 Reserved Reserved RXDET_A_1 RXDET_A_0
SMBus Register 0x0B [3] 0x0B [2] 0x0B [1] 0x0B [0] 0x0E [5] 0x0E [4] 0x0E [3] 0x0E [2]
Value 00 0 0 0 0 0 0 0 0
Description 8 Reserved Reserved Reserved Reserved Reserved Reserved CHA_EQ_1 CHA_EQ_0
SMBus Register 0x0F [7] 0x0F [6] 0x0F [5] 0x0F [4] 0x0F [3] 0x0F [2] 0x0F [1] 0x0F [0]
Value 2F 0 0 1 0 1 1 1 1
Description 9 CHA_SCP Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x10 [7] 0x10 [6] 0x10 [5] 0x10 [4] 0x10 [3] 0x10 [2] 0x10 [1] 0x10 [0]
Value ED 1 1 1 0 1 1 0 1
Description A CHA_VOD_DB_2 CHA_VOD_DB_1 CHA_VOD_DB_0 Reserved CHA_THa_1 CHA_THa_0 CHA_THd_1 CHA_THd_0
SMBus Register 0x11 [2] 0x11 [1] 0x11 [0] 0x12 [7] 0x12 [3] 0x12 [2] 0x12 [1] 0x12 [0]
Value 40 0 1 0 0 0 0 0 0
Description B Reserved Reserved RXDET_B_1 RXDET_B_0 Reserved Reserved Reserved Reserved
SMBus Register 0x15 [5] 0x15 [4] 0x15 [3] 0x15 [2] 0x16 [7] 0x16 [6] 0x16 [5] 0x16 [4]
Value 02 0 0 0 0 0 0 1 0
Description C Reserved Reserved CHB_EQ_1 CHB_EQ_0 CHB_SCP Reserved Reserved Reserved
SMBus Register 0x16 [3] 0x16 [2] 0x16 [1] 0x16 [0] 0x17 [7] 0x17 [6] 0x17 [5] 0x17 [4]
Value FE 1 1 1 1 1 1 1 0
Description D Reserved Reserved Reserved Reserved CHB_VOD_DB_2 CHB_VOD_DB_1 CHB_VOD_DB_0 Reserved
SMBus Register 0x17 [3] 0x17 [2] 0x17 [1] 0x17 [0] 0x18 [2] 0x18 [1] 0x18 [0] 0x19 [7]
Value D4 1 1 0 1 0 1 0 0
Description E CHB_THa_1 CHB_THa_0 CHB_THd_1 CHB_THd_0 Reserved Reserved Reserved Reserved
SMBus Register 0x19 [3] 0x19 [2] 0x19 [1] 0x19 [0] 0x1C [5] 0x1C [4] 0x1C [3] 0x1C [2]
Value 00 0 0 0 0 0 0 0 0
Description F Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x1D [7] 0x1D [6] 0x1D [5] 0x1D [4] 0x1D [3] 0x1D [2] 0x1D [1] 0x1D [0]
Value 2F 0 0 1 0 1 1 1 1
Description 10 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x1E [7] 0x1E [6] 0x1E [5] 0x1E [4] 0x1E [3] 0x1E [2] 0x1E [1] 0x1E [0]
Value AD 1 0 1 0 1 1 0 1
Description 11 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x1F [2] 0x1F [1] 0x1F [0] 0x20 [7] 0x20 [3] 0x20 [2] 0x20 [1] 0x20 [0]
Value 40 0 1 0 0 0 0 0 0
Description 12 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x23 [5] 0x23 [4] 0x23 [3] 0x23 [2] 0x24 [7] 0x24 [6] 0x24 [5] 0x24 [4]
Value 02 0 0 0 0 0 0 1 0
Description 13 Reserved Reserved Reserved Reserved Reserved Reserved Reserved CHA_VOD_2
SMBus Register 0x24 [3] 0x24 [2] 0x24 [1] 0x24 [0] 0x25 [7] 0x25 [6] 0x25 [5] 0x25 [4]
Value FA 1 1 1 1 1 0 1 0
Description 14 CHA_VOD_1 CHA_VOD_0 Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x25 [3] 0x25 [2] 0x25 [1] 0x25 [0] 0x26 [2] 0x26 [1] 0x26 [0] 0x27 [7]
Value D4 1 1 0 1 0 1 0 0
Description 15 Reserved Reserved Reserved Reserved ovrd_fast_idle hi_idle_th CHA hi_idle_th CHB fast_idle CHA
SMBus Register 0x27 [3] 0x27 [2] 0x27 [1] 0x27 [0] 0x28 [6] 0x28 [5] 0x28 [4] 0x28 [3]
Value 00 0 0 0 0 0 0 0 0
Description 16 fast_idle CHB low_gain CHA low_gain CHB Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x28 [2] 0x28 [1] 0x28 [0] 0x2B [5] 0x2B [4] 0x2B [3] 0x2B [2] 0x2C [7]
Value 00 0 0 0 0 0 0 0 0
Description 17 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x2C [6] 0x2C [5] 0x2C [4] 0x2C [3] 0x2C [2] 0x2C [1] 0x2C [0] 0x2D [7]
Value 5F 0 1 0 1 1 1 1 1
Description 18 Reserved Reserved CHB_VOD_2 CHB_VOD_1 CHB_VOD_0 Reserved Reserved Reserved
SMBus Register 0x2D [6] 0x2D [5] 0x2D [4] 0x2D [3] 0x2D [2] 0x2D [1] 0x2D [0] 0x2E [2]
Value 5A 0 1 0 1 1 0 1 0
Description 19 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x2E [1] 0x2E [0] 0x2F [7] 0x2F [3] 0x2F [2] 0x2F [1] 0x2F [0] 0x32 [5]
Value 80 1 0 0 0 0 0 0 0
Description 1A Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x32 [4] 0x32 [3] 0x32 [2] 0x33 [7] 0x33 [6] 0x33 [5] 0x33 [4] 0x33 [3]
Value 05 0 0 0 0 0 1 0 1
Description 1B Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x33 [2] 0x33 [1] 0x33 [0] 0x34 [7] 0x34 [6] 0x34 [5] 0x34 [4] 0x34 [3]
Value F5 1 1 1 1 0 1 0 1
Description 1C Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x34 [2] 0x34 [1] 0x34 [0] 0x35 [2] 0x35 [1] 0x35 [0] 0x36 [7] 0x36 [3]
Value A8 1 0 1 0 1 0 0 0
Description 1D Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x36 [2] 0x36 [1] 0x36 [0] 0x39 [5] 0x39 [4] 0x39 [3] 0x39 [2] 0x3A [7]
Value 00 0 0 0 0 0 0 0 0
Description 1E Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x3A [6] 0x3A [5] 0x3A [4] 0x3A [3] 0x3A [2] 0x3A [1] 0x3A [0] 0x3B [7]
Value 5F 0 1 0 1 1 1 1 1
Description 1F Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x3B [6] 0x3B [5] 0x3B [4] 0x3B [3] 0x3B [2] 0x3B [1] 0x3B [0] 0x3C [2]
Value 5A 0 1 0 1 1 0 1 0
Description 20 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x3C [1] 0x3C [0] 0x3D [7] 0x3D [3] 0x3D [2] 0x3D [1] 0x3D [0] 0x40 [5]
Value 80 1 0 0 0 0 0 0 0
Description 21 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x40 [4] 0x40 [3] 0x40 [2] 0x41 [7] 0x41 [6] 0x41 [5] 0x41 [4] 0x41 [3]
Value 05 0 0 0 0 0 1 0 1
Description 22 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x41 [2] 0x41 [1] 0x41 [0] 0x42 [7] 0x42 [6] 0x42 [5] 0x42 [4] 0x42 [3]
Value F5 1 1 1 1 0 1 0 1
Description 23 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x42 [2] 0x42 [1] 0x42 [0] 0x43 [2] 0x43 [1] 0x43 [0] 0x44 [7] 0x44 [3]
Value A8 1 0 1 0 1 0 0 0
Description 24 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
SMBus Register 0x44 [2] 0x44 [1] 0x44 [0] 0x47 [3] 0x47 [2] 0x47 [2] 0x47 [0] 0x48 [7]
Value 00 0 0 0 0 0 0 0 0
Description 25 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]
Value 00 0 0 0 0 0 0 0 0
Description 26 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]
Value 54 0 1 0 1 0 1 0 0
Description 27 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]
Value 54 0 1 0 1 0 1 0 0

Table 7. Example of EEPROM For Four Devices Using Two Address Maps

EEPROM ADDRESS EEPROM DATA COMMENTS
DECIMAL HEX
0 00 0x43 CRC_EN = 0, Address Map = 1, > 256 bytes = 0, Device Count[3:0] = 3
1 01 0x00
2 02 0x08 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 0x03 EQ CHA = 03
17 11 0xED
18 12 0x00 VOD_DB CHA = 0 (0dB)
19 13 0x00
20 14 0xFE EQ CHB = 03
21 15 0xD0 VOD_DB CHB = 0 (0dB)
22 16 0x00
23 17 0x2F
24 18 0xAD
25 19 0x40
26 1A 0x02
27 1B 0xFB VOD CHA = 1.4 V
28 1C 0xD4 VOD CHA = 1.4 V
29 1D 0x00 Signal Detect Status Threshold Control
30 1E 0x00 Signal Detect status Threshold Control
31 1F 0x5F
32 20 0x7A VOD CHB = 1.4 V
33 21 0x80
34 22 0x05
35 23 0xF5
36 24 0xA8
37 25 0x00
38 26 0x5F
39 27 0x5A
40 28 0x80
41 29 0x05
42 2A 0xF5
43 2B 0xA8
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 CHA = 01
54 36 0xED
55 37 0x00 VOD_DB CHA = 0 (0dB)
56 38 0x00
57 39 0xFE EQ CHB = 03
58 3A 0xD0 VOD_DB CHB1 = 0 (0dB)
59 3B 0x00
60 3C 0x2F
61 3D 0xAD
62 3E 0x40
63 3F 0x02
64 40 0xFB VOD CHA = 1.4 V
65 41 0xD4 VOD CHA = 1.4 V
66 42 0x00 Signal Detect status Threshold Control
67 43 0x00 Signal Detect status Threshold Control
68 44 0x5F
69 45 0x7A VOD CHB = 1.4 V
70 46 0x80
71 47 0x05
72 48 0xF5
73 49 0xA8
74 4A 0x00
75 4B 0x5F
76 4C 0x5A
77 4D 0x80
78 4E 0x05
79 4F 0xF5
80 50 0xA8
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). EEPROM must support 1 MHz operation.

8.6 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 DS125BR111 has the AD[3:0] inputs in SMBus mode. These pins are the user set SMBus slave address inputs. The AD[3:0] Pins have internal pull-down. Based on the SMBus 2.0 specification, the DS125BR111 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, the device default address byte is 0xB0.The device supports up to 16 address byte, which can be set with the AD[3:0] inputs. Below are the 16 addresses. Use the address listed in the Slave Address Byte column to address.

Table 8. Device Slave Address Bytes

AD[3:0] SETTINGS FULL SLAVE ADDRESS BYTE (HEX) 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 5 V tolerant. 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.

8.6.1 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.

8.6.2 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.

8.6.3 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.

8.6.4 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.

8.6.5 SMBus Register Information

Table 9. SMBus Register Map

ADDRESS REGISTER NAME BITS FIELD TYPE DEFAULT EEPROM REG BIT DESCRIPTION
0x00 Device ID 7 Reserved R/W 0x00 Set bit to 0
[6:3] SMBus strap observation
6:3 I2C Address [3:0] R
2 EEPROM reading done R 1 = EEPROM Done Loading
0 = EEPROM Loading
1:0 Reserved RWSC Set bits to 0
0x01 Control 1 7:2 Reserved R/W 0x00 Yes Set bits to 0
1:0 ENABLE A/B [1]: Disable Channel B (1); Normal Operation (0)
[0]: Disable Channel A (1); Normal Operation (0)
Note: Must set ENABLE override in Reg 0x02[0]
0x02 Control 2 7 Override PWDN R/W 0x00 [1]: Override PWDN (1); PWDN pin control (0)
6 PWDN Pin value Override value for PWDN pin
[1]: PWDN - Low Power (1); Normal Operation (0)
Note: Must set PWDN override in Reg 0x02[7]
5:4 Reserved Yes Set bits to 0
3 PWDN Inputs Yes Set bit to 0
2 PWDN Oscillator Yes Set bit to 0
1 Reserved Set bit to 0
0 Override ENABLE Yes 1 = Enables Reg 0x01[1:0]
0 = Normal Operation
0x04 Reserved 7:0 Reserved R/W 0x00 Yes Set bits to 0
0x05 Reserved 7:0 Reserved R/W 0x00 Reserved
0x06 SMBus Control 7:5 Reserved R/W 0x10 Set bits to 0
4 Reserved Yes Set bit to 1
3 Register Mode Enable 1 = Enable SMBus Slave Mode Register Control
0 = Disable Register Control
Note: With register control "Enabled" register updates take immediate effect on high speed data path. When "Disabled", SMBus registers are still R/W, but changes will not be sent to the high speed controls until this register is "Enabled".
2:0 Reserved Set bits to 0
0x07 Digital Reset and Control 7 Reserved R/W 0x01 Set bit to 0
6 Reset Regs RWSC Self clearing reset for registers.
Writing a [1] will return register settings to default values.
5 Reset SMBus Master RWSC Self clearing reset to SMBus master state machine
4:0 Reserved R/W Set bits to 0001'b
0x08 Pin Override 7 Reserved R/W 0x00 Set bit to 0
6 Override SD_TH Threshold Yes 1 = Override by Channel - see Reg 0x12 and 0x19
0 = SD_TH pin control
5:4 Reserved Yes Set bits to 0
3 Override RXDET Yes 1 = Override by Channel - see Reg 0x0E and 0x15
0 = RXDET pin control
2:0 Reserved Yes Set bits to 0
0x0A Signal Detect Status 7:2 Reserved R 0x00
1 Internal Idle B R 1 = LOS (No Signal Present)
0 = Signal present
Note: RES Pin = Float for these bits to function.
0 Internal Idle A
0x0B Reserved 7:0 Reserved R/W 0x70 Yes
0x0C Reserved 7:0 Reserved R/W 0x00 Set bits to 0
0x0E CH A
RXDET Control		 7:5 Reserved R/W 0x00 Set bits to 0
4 Reserved Yes Set bit to 0
3:2 RXDET Yes CHA RXDET register control
00'b = Input is high-z impedance
01'b = Auto RX-Detect, outputs test every 12 ms for 600 ms (50 times) then stops; termination is high-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 high-z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: override RXDET pin in 0x08[3].
Note: Can only be used with the register write sequence described in .PCIe Applications
1:0 Reserved Set bits to 0
0x0F CH A
EQ Control		 7:0 BOOST [7:0] R/W 0x2F Yes EQ Control - total of 4 levels
See Table 4
0x10 CH A
Control		 7 Select Short Circuit Protection R/W 0xED Yes 1 = Short Circuit Protection ON
0 = Short Circuit Protection OFF
6 Reserved Yes Set bit to 0
5:3 Reserved Yes Set bits to 0
2:0 Reserved Yes Set bits to 101'b
0x11 CH A
VOD_DB Control		 7 Reserved R 0x82
6:5 Reserved
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control [2:0] Yes OUTA VOD_DB Control (010'b Default). Based on system interoperability testing it is recommended to set these bits to 000'b for SAS, PCIe, and other non-limiting applications.
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 gain by a factor of the corresponding amount of dB reduction.
0x12 CH A
SD Threshold		 7 Reserved R/W 0x00 Yes Set bit to 0
6:4 Reserved Set bits to 0
3:2 Signal Detect Status
Tassert		 Yes Assert Thresholds (1010 pattern 12 Gbps)
Use only if register 0x08 [6] = 1
00'b = 50 mV (Default)
01'b = 40 mV
10'b = 75 mV
11'b = 58 mV
Note: Override the SD_TH pin using 0x08[6].
Note: This threshold adjustment is for SD status indication only.
1:0 Signal Detect Status
Tde-assert		 Yes De-assert Thresholds (1010 pattern 12 Gbps)
Use only if register 0x08 [6] = 1
00'b = 37 mV (Default)
01'b = 22 mV
10'b = 55 mV
11'b = 45 mV
Note: Override the SD_TH pin using 0x08[6].
Note: This threshold adjustment is for SD status indication only.
0x13 Reserved 7:2 Reserved R/W 0x00 Set bits to 0
1:0 R
0x14 CH B
7:3 Reserved R/W 0x00 Set bits to 0
2 Signal Detect Reset 1 = Override Signal Detect, hold "Off"
1 Signal Detect Preset 1 = Override Signal Detect, hold "On"
0 Reserved Set bit to 0
0x15 CH B
RXDET Control		 7:5 Reserved R/W 0x00 Set bits to 0
4 Reserved Yes Set bit to 0
3:2 RXDET Yes CHB RXDET register control
00'b = Input is high-z impedance
01'b = Auto RX-Detect, outputs test every 12 ms for 600 ms (50 times) then stops; termination is high-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 high-z until detection; once detected input termination is 50 Ω
11'b = Input is 50 Ω
Note: override RXDET pin in 0x08[3].
Note: Can only be used with the register write sequence described in PCIe Applications .
1:0 Reserved Set bits to 0
0x16 CH B
EQ Control		 7:0 BOOST [7:0] R/W 0x2F Yes EQ Control - total of 4 levels
See Table 4
0x17 CH B
RATE Control		 7 Select Short Circuit Protection R/W 0xED Yes 1 = Short Circuit Protection ON
0 = Short Circuit Protection OFF
6 Reserved Set bit to 0
5:3 Reserved Set bits to 0
2:0 Reserved Set bits to 101'b
0x18 CH B
VOD_DB Control		 7 Reserved R 0x82
6:5 Reserved
4:3 Reserved R/W Set bits to 0
2:0 VOD_DB Control [2:0] Yes OUTB VOD_DB Control (010'b Default). Based on system interoperability testing it is recommended to set these bits to 000'b for SAS, PCIe, and other non-limiting applications.
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 gain by a factor of the corresponding amount of dB reduction.
0x19 CH B
SD Threshold		 7 Reserved R/W 0x00 Yes Set bits to 0
6:4 Reserved
3:2 Signal Detect Status
Tassert		 Yes Assert Thresholds (1010 pattern 12 Gbps)
Use only if register 0x08 [6] = 1
00'b = 50 mV (Default)
01'b = 40 mV
10'b = 75 mV
11'b = 58 mV
Note: Override the SD_TH pin using 0x08[6].
Note: This threshold adjustment is for SD status indication only.
1:0 Signal Detect Status
Tde-assert		 Yes De-assert Thresholds (1010 pattern 12 Gbps)
Use only if register 0x08 [6] = 1
00'b = 37 mV (Default)
01'b = 22 mV
10'b = 55 mV
11'b = 45 mV
Note: Override the SD_TH pin using 0x08[6].
Note: This threshold adjustment is for SD status indication only.
0x1C 7:6 Reserved R/W 0x00 Set bits to 0
5:2 Yes
1:0
0x1D 7:0 Reserved R/W 0x2F Yes
0x1E 7:0 Reserved R/W 0xAD Yes
0x1F 7:3 Reserved R/W 0x02
2:0 Yes
0x20 7 Reserved R/W 0x00 Yes
6:4
3:0 Yes
0x23 7:6 Reserved R/W 0x00
5:2 Yes
1:0
0x24 7:0 Reserved R/W 0x2F Yes
0x25 CH A VOD 7:5 Reserved R/W 0xAD Yes Set bits to 101'b
4:2 VOD CHA Control VOD Control CHA: VOD / VID Ratio
000'b = 0.65
001'b = 0.70
010'b = 0.78
011'b = 0.83
100'b = 0.88
101'b = 0.91 (Default)
110'b = 1.00 (Recommended for SAS/SATA/PCIe)
111'b = 1.05 (Recommended for SAS/SATA/PCIe)
1:0 Reserved Set bits to 01'b
0x26 7:6 Reserved R 0x02
4:3 R/W
2:0 Yes
0x27 7 Reserved R/W 0x00 Yes
6:4
3:0 Yes
0x28 Signal Detect Control 7 Reserved R/W 0x00 Set bit to 0
6 Override Fast IDLE Yes Override Fast IDLE
1 = Use value in 0x28[3:2]
0 = Based on MODE pin
5:4 High IDLE Yes Enable higher SD Threshold range
[1]: CH A
[0]: CH B
3:2 Fast IDLE Yes Enable Fast SD response
[1]: CH A
[0]: CH B
1:0 Reduced SD Gain Yes Enable reduced SD Gain
[1]: CH A
[0]: CH B
0x2B 7:6 Reserved R/W 0x00
5:2 Yes
1:0
0x2C 7:0 Reserved R/W 0x2F Yes
0x2D CH B VOD 7:5 Reserved R/W 0xAD Yes Set bits to 101'b
4:2 VOD CHB Control VOD Control CHB: VOD / VID Ratio
000'b = 0.65
001'b = 0.70
010'b = 0.78
011'b = 0.83
100'b = 0.88
101'b = 0.91 (Default)
110'b = 1.00 (Recommended for SAS/SATA/PCIe)
111'b = 1.05 (Recommended for SAS/SATA/PCIe)
1:0 Reserved Set bits to 01'b
0x2E 7:5 Reserved R 0x02
4:3 R/W
2:0 Yes
0x2F 7 Reserved R/W 0x00 Yes
6:4
3:0 Yes
0x32 7:6 Reserved R/W 0x00
5:2 Yes
1:0
0x33 7:0 Reserved R/W 0x2F Yes
0x34 7:0 Reserved R/W 0xAD Yes
0x35 7:5 Reserved R 0x02
4:3 R/W
2:0 Yes
0x36 7 Reserved R/W 0x00 Yes
6:4
3:0 Yes
0x39 7:6 Reserved R/W 0x00
5:2 Yes
1:0
0x3A 7:0 Reserved R/W 0x2F Yes
0x3B 7:0 Reserved R/W 0xAD Yes
0x3C 7:5 Reserved R 0x02
4:3 R/W
2:0 Yes
0x3D 7 Reserved R/W 0x00 Yes
6:4
3:0 Yes
0x40 7:6 Reserved R/W 0x00
5:2 Yes
1:0
0x41 7:0 Reserved R/W 0x2F Yes
0x42 7:0 Reserved R/W 0xAD Yes
0x43 7:5 Reserved R 0x02
4:3 R/W
2:0 Yes
0x44 7 Reserved R/W 0x00 Yes
6:4
3:0 Yes
0x47 7:4 Reserved R/W 0x00
3:0 Yes
0x48 7:6 Reserved R/W 0x05 Yes
5:0
0x4C 7:3 Reserved R/W 0x00 Yes
2:1
0 Yes
0x51 Device Information 7:5 Version R 0x97 100'b
4:0 Device ID 1 0111'b
0x59 7:1 Reserved R/W 0x00
0 Yes
0x5A 7:0 Reserved R/W 0x54 Yes
0x5B 7:0 Reserved R/W 0x54 Yes
Legend:
RWSC: Read / Write / Self Clearing on Read
R/W: Read / Write
R: Read Only