F-Tile Architecture and PMA and FEC Direct PHY IP User Guide

ID 683872
Date 11/04/2024
Public
Document Table of Contents

3.14.2.1.1. Direct Register Method Examples

The following examples demonstrate the direct register method to configure the FGT PMA.

TX Equalizer Co-efficients

To set the TX equalizer co-efficients:
  • Write the TX equalizer pre_tap_2 register (0x47830[18:16]) with valid value.
  • Write the TX equalizer pre_tap_1 register (0x47830[9:5]) with valid value.
  • Write the TX equalizer main_tap register (0x47830[15:10]) with valid value.
  • Write the TX equalizer post_tap_1 register (0x47830[4:0]) with valid value.

Mute TX Output

To mute TX output (make TX output 0v):
  • Write 2’b11 to 0x41750[25:24]
To unmute TX output:
  • Write 2’b00 to 0x41750[25:24]

Internal Serial Loopback

Cache calibration registers listed in Appendix A.3. 40

To enable internal serial loopback:
  • Write calibration registers with values listed in Appendix A.3. 40
  • Write 0x0 to 0x41418[31]
  • Write 0x1 to 0x41420[25]
  • Write 0x1 to 0x41418[29]
  • Write 0x1 to 0x41418[31]
To disable internal serial loopback:
  • Write calibration registers with cached values.40
  • Write 0x0 to 0x41418[31]
  • Write 0x0 to 0x41418[29]
  • Write 0x0 to 0x41420[25]

Reverse Parallel Loopback

To enable the Reverse Parallel Loopback:
  • Wait for rx_ready assert
  • Assert TX reset
  • Wait for TX reset Ack
  • Write 0x0 to 0x41830[31:0]
  • Write 0x0 to 0x41768[24]
  • Write 0x1 to 0x41414[29]
  • Write 0x1 to 0x4141C[30]
  • Write 0x1 to 0x41418[31]
  • Deassert TX reset
  • Wait for TX reset ACK deassert
  • If FEC is enabled, you must respond to the tx_am_gen_start signal and generate the tx_am_gen_2x_ack pulse to get tx_ready to assert. This step is also needed when you use the F-Tile Transceiver Toolkit to enable the RX to TX reverse parallel loopback.
To disable the Reverse Parallel Loopback:
  • Assert TX reset
  • Write 0x3 to 0x41830[31:0]
  • Write 0x1 to 0x41768[24]
  • Write 0x0 to 0x41414[29]
  • Write 0x0 to 0x4141C[30]
  • Write 0x0 to 0x41418[31]
  • Deassert TX reset
  • Wait for TX reset ACK deassert
  • If FEC is enabled, you must respond to the tx_am_gen_start signal and generate the tx_am_gen_2x_ack pulse to get tx_ready to assert. This step is also needed when you use the F-Tile Transceiver Toolkit to disable the RX to TX reverse parallel loopback.

TX to RX Parallel Loopback

To enable the TX to RX Parallel Loopback:
  • Write 0x1 to 0x416A4[8]
  • Write 0x1 to 0x41418[31]
To disable the TX to RX Parallel Loopback:
  • Write 0x0 to 0x416A4[8]
  • Write 0x0 to 0x41418[31]

Polarity Inversion

TX polarity inversion:
  • Write 0x1 to 0x41428[7]
TX polarity inversion revert back:
  • Write 0x0 to 0x41428[7]
RX polarity inversion:
  • Write 0x1 to 0x41428[6]
RX polarity inversion revert back:
  • Write 0x0 to 0x41428[6]

Measuring the Bit Error Rate (BER) with FGT PMAs

  1. Check that the RX link is ready for the desired lane:
    1. Read 0x814[31:16] 41 to confirm that the corresponding lane's rx_cdr_locked2data = 1
  2. Assign the PRBS pattern value:
    1. For TX:
      1. Set valid values to 0x416AC[31:28]
    2. For RX:
      1. Set valid values to 0x41428[3:0]
    3. Valid values for PRBS pattern:
      • UDP : 0x0
      • PRBS7 : 0x1
      • PRBS9 : 0x2
      • PRBS11 : 0x3
      • PRBS13 : 0x4
      • PRBS15 : 0x5
      • PRBS23 : 0x6
      • PRBS28 : 0x7
      • PRBS31 : 0x8
      • QPRBS13 : 0x9
      • PRBS13Q : 0xa
      • PRBS31Q : 0xb
      • SSPR : 0xc
      • SSPR1 : 0xd
      • SSPRQ : 0xe
  3. BER Start:
    1. Write 0x1 to 0x416AC[23]
    2. Write 0x1 to 0x41424[26]
    3. Write 0x3 to 0x4176C[28:27]
    4. Write 0x3 to 0x415B4[19:18]
  4. Inject one bit of error (repeat the following two steps multiple times to inject multiple bits of error):
    1. Write 0x1 to 0x416AC[22]
    2. Write 0x0 to 0x416AC[22]
  5. Error Count:
    1. Read from 0x41444[31:0]
  6. To check overflow, read 0x4143C[21], 1 = overflow, 0 = no overflow
  7. To clear the counter, toggle 0x415B4[19:18]:
    1. Write 0x0 to 0x415B4[19:18]
    2. Write 0x3 to 0x415B4[19:18]
  8. BER Stop:
    1. Write 0x0 to 0x416AC[23]
    2. Write 0x0 to 0x41424[26]
    3. Write 0x0 to 0x4176C[28:27]
    4. Write 0x0 to 0x415B4[19:18]
The sequence is valid only when RX manual tuning is used (RX auto adaptation is bypassed). If RX auto adaptation is used, use the FGT attribute access method.
40 This step is optional and you only need it when an external signal is present on the receiver's input.
41 Address 0x814 is part of the PMA and FEC soft CSR register.