CertusPro-NX SerDes/PCS Usage Guide
Preliminary
Technical Note
FPGA-TN-02245-0.81
© 2020-2021 Lattice Semiconductor
129
All rights reserved. CONFIDENTIAL
Table A. 21. PRBS Error Counter Register [reg65]
Field
Name
Access
Width
Reset
Description
[7:0]
prbs_errcnt
RO
8
8’h00
Reports the number of PRBS error detected when the
PRBS test is applied. This register is automatically cleared
when the prbs_chk bit gets cleared. The PRBS error
counter saturates at 254 errors, the 255-count value
corresponding to an error code where the CDR PLL is not
locked to incoming data. In case of such error code
detected, the PRBS test must either wait for longer time
for CDR PLL to synchronize on input data before enabling
PRBS checker, or simply times out reporting that no data is
received at all. Note that the PRBS error counter logic is
also with count error, when the PRBS invariant (all zero
value) is obtained, considering input data as error data.
Table A. 22. PHY Reset Override Register [reg66]
Field
Name
Access
Width
Reset
Description
[7]
rxhf_clkdn
RW
1
1’b0
CDR PLL VCO control.
1’b1 – disables CDR PLL VCO and shuts down the Rx
de-serializer circuitry and RxClk while still maintaining
CDR PLLs in lock for intermediate power savings.
1’b0 – normal operation.
[6]
txhf_clkdn
RW
1
1’b0
Tx PLL VCO control
1’b1 – disables CDR PLL VCO and shuts down the Tx
high frequency trees and TxClk while still maintaining Tx
PLLs in lock for intermediate power savings.
1’b0 – normal operation.
[5]
rxpllrst
RW
1
1’b0
1’b1 – reset the CDR PLL settings.
1’b0 – normal operation.
[4]
txpllrst
RW
1
1’b0
1’b1 – reset the Tx PLL settings.
1’b0 – normal operation.
[3]
rxpll_init
RW
1
1’b0
1’b1 – initializes the CDR PLL settings.
1’b0 – normal operation.
[2]
txpll_init
RW
1
1’b0
1’b1 – initializes the Tx PLL settings.
1’b0 – normal operation.
[1]
rx_hiz
RW
1
1’b0
1’b1 – forces Rx driver to HiZ.
1’b0 – normal operation.
[0]
tx_hiz
RW
1
1’b0
1’b1 – forces Tx driver to HiZ.
1’b0 – normal operation.
Table A. 23. PHY Power Override Register [reg67]
Field
Name
Access
Width
Reset
Description
[7:1]
reserved
RSVD
7
7’h0
—
[0]
rx_pwrdn
RW
1
1’b0
Force the Rx PMA logic to be in power-down mode.
1’b1 – power down Rx PMA.
1’b0 – normal operation.
Table A. 24. Transmit PLL Current Charge Pump [reg69]
Field
Name
Access
Width
Reset
Description
[7:3]
reserved
RSVD
5
5’h0
—
[2:0]
txicp_rate
RW
3
3’b101
These bits define the Tx PLL charge pump current when
the PMA is running in PCIe Gen1 speed or in any other