SNLS398H January   2012  – February 2018 DS125DF410

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Typical Application Diagram
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Data Path Operation
      2. 7.3.2 Signal Detect
      3. 7.3.3 CTLE
      4. 7.3.4 DFE
      5. 7.3.5 Clock and Data Recovery
      6. 7.3.6 Output Driver
      7. 7.3.7 Device Configuration
        1. 7.3.7.1 Rate and Subrate Setting
    4. 7.4 Device Functional Modes
      1. 7.4.1 SMBus Master Mode and SMBus Slave Mode
      2. 7.4.2 Address Lines <ADDR_[3:0]>
      3. 7.4.3 SDA and SDC
      4. 7.4.4 Standards-Based Modes
        1. 7.4.4.1 Ref_mode 3 Mode (Reference Clock Required)
        2. 7.4.4.2 False Lock Detector Setting
        3. 7.4.4.3 Reference Clock In
        4. 7.4.4.4 Reference Clock Out
        5. 7.4.4.5 Driver Output Voltage
        6. 7.4.4.6 Driver Output De-Emphasis
        7. 7.4.4.7 Driver Output Rise/Fall Time
        8. 7.4.4.8 INT
        9. 7.4.4.9 LOCK_3, LOCK_2, LOCK_1, and LOCK_0
    5. 7.5 Programming
      1. 7.5.1  SMBus Strap Observation
      2. 7.5.2  Device Revision and Device ID
      3. 7.5.3  Control/Shared Register Reset
      4. 7.5.4  Interrupt Channel Flag Bits
      5. 7.5.5  SMBus Master Mode Control Bits
      6. 7.5.6  Resetting Individual Channels of the Retimer
      7. 7.5.7  Interrupt Status
      8. 7.5.8  Overriding the CTLE Boost Setting
      9. 7.5.9  Overriding the VCO Search Values
      10. 7.5.10 Overriding the Output Multiplexer
      11. 7.5.11 Overriding the VCO Divider Selection
      12. 7.5.12 Using the PRBS Generator
      13. 7.5.13 Using the Internal Eye Opening Monitor
      14. 7.5.14 Overriding the DFE Tap Weights and Polarities
      15. 7.5.15 Enabling Slow Rise/Fall Time on the Output Driver
      16. 7.5.16 Inverting the Output Polarity
      17. 7.5.17 Overriding the Figure of Merit for Adaptation
      18. 7.5.18 Setting the Rate and Subrate for Lock Acquisition
      19. 7.5.19 Setting the Adaptation/Lock Mode
      20. 7.5.20 Initiating Adaptation
      21. 7.5.21 Setting the Reference Enable Mode
      22. 7.5.22 Overriding the CTLE Settings Used for CTLE Adaptation
      23. 7.5.23 Setting the Output Differential Voltage
      24. 7.5.24 Setting the Output De-Emphasis Setting
    6. 7.6 Register Maps
      1. 7.6.1 Register Information
      2. 7.6.2 Bit Fields in the Register Set
      3. 7.6.3 Writing to and Reading from the Control/Shared Registers
      4. 7.6.4 Channel Select Register
      5. 7.6.5 Reading to and Writing from the Channel Registers
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  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 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.5.22 Overriding the CTLE Settings Used for CTLE Adaptation

Register 0x2c, bits 3:0, Register 0x2f, bit 3, Register 0x39, bits 4:0, and Registers 0x50-0x5f

The CTLE adaptation algorithm operates by setting the CTLE boost stage controls to a set of pre-determined boost settings, each of which provides progressively more high-frequency boost. At each stage in the adaptation process, the DS125DF410 attempts to phase lock to the equalized signal. If the phase lock succeeds, the DS125DF410 measures the horizontal and vertical eye openings using the internal eye monitor circuit. The DS125DF410 computes a figure of merit for the eye opening and compares it to the previous best value of the figure of merit. While the figure of merit continues to improve, the DS125DF410 continues to try additional values of the CTLE boost setting until the figure of merit ceases to improve and begins to degrade. When the figure of merit starts to degrade, the DS125DF410 still continues to try additional CTLE settings for a pre-determined trial count called the “look-beyond” count, and if no improvement in the figure of merit results, it resets the CTLE boost values to those that produced the best figure of merit. The resulting CTLE boost values are then stored in register 0x03. The “look-beyond” count is configured by the value in register 0x2c, bits 3:0. The value is 0x2 by default.

The set of boost values used as candidate values during CTLE adaptation are stored as bit fields in registers 0x40-0x5f. The default values for these settings are shown in Table 11. These values may be overridden by setting the corresponding register values over the SMBus. If these values are overridden, then the next time the CTLE adaptation is performed the set of CTLE boost values stored in these registers will be used for the adaptation. Resetting the channel registers by setting bit 2 of channel register 0x00 will reset the CTLE boost settings to their defaults. So will power-cycling the DS125DF410.

Table 11. CTLE Settings for Adaptation

Register (Hex)Bits 7:6 (CTLE Stage 0)Bits 5:4 (CTLE Stage 1)Bits 3:2 (CTLE Stage 2)Bits 1:0 (CTLE Stage 3)CTLE Boost StringCTLE Adaptation Index
40 0 0 0 0 0000 0
41 0 0 0 1 0001 1
42 0 0 1 0 0010 2
43 0 1 0 0 0100 3
44 1 0 0 0 1000 4
45 0 0 2 0 0020 5
46 0 0 0 2 0002 6
47 2 0 0 0 2000 7
48 0 0 0 3 0003 8
49 0 0 3 0 0030 9
4A 0 3 0 0 0300 10
4B 1 0 0 1 1001 11
4C 1 1 0 0 1100 12
4D 3 0 0 0 3000 13
4E 1 2 0 0 1200 14
4F 2 1 0 0 2100 15
50 2 0 2 0 2020 16
51 2 0 0 2 2002 17
52 2 2 0 0 2200 18
53 1 0 1 2 1012 19
54 1 1 0 2 1102 20
55 2 0 3 0 2030 21
56 2 3 0 0 2300 22
57 3 0 2 0 3020 23
58 1 1 1 3 1113 24
59 1 1 3 1 1131 25
5A 1 2 2 1 1221 26
5B 1 3 1 1 1311 27
5C 3 1 1 1 3111 28
5D 2 1 2 1 2121 29
5E 2 1 1 2 2112 30
5F 2 2 1 1 2211 31

As an alternative to, or in conjunction with, writing the CTLE boost setting registers 0x40 through 0x5f, it is possible to set the starting CTLE boost setting index. To override the default setting, which is 0, set bit 3 of register 0x2f. When this bit is set, the starting index for adaptation comes from register 0x39, bits 4:0. This is the index into the CTLE settings table in registers 0x40 through 0x5f. When this starting index is 0, which is the default, CTLE adaptation starts at the first setting in the table, the one in register 0x40, and continues until the optimum FOM is reached.