01-29-2018 01:43 AM
I use GTP RX and set RX_CM_SEL[1:0] = 2'b10 (float mode) in my design,
I don't know how to set GTP RXLPM_INCM_CFG and RXLPM_IPCM_CFG for different VCM,
My design need receive differential signal with VCM possible range from 0.3V to 0.9V (not dynamic change),
I have read below AR but not suitable for my application,
https://www.xilinx.com/support/answers/51448.html
What is the VCM ranges for RXLPM_INCM_CFG and RXLPM_IPCM_CFG?
Does only one of RXLPM_INCM_CFG and RXLPM_IPCM_CFG must set to 1'b1 (can not both set to 1'b1 or 1'b0)?
Thank You~
01-30-2018 11:47 AM - edited 01-30-2018 12:01 PM
hello,
The AC-coupling is recommended. If you must use the DC-coupling, please be careful with common mode currents. The receiver bias should match the signal common mode and the two ports
RXLPM_INCM_CFG
RXLPM_IPCM_CFG
are needed to enable the high/low common mode operation.
I do not find a characterization for common mode from 0.3V to <0.8V
At 0.3V I would try with
RXLPM_INCM_CFG = 0
RXLPM_IPCM_CFG = 1
RX_CM_TRIM [3:0] = 4’b0011 – 300 mV
RX_CM_SEL [1:0] = 2'b11
Because it is very close to Use mode 1 (table 4-3). Unfortunately I have no additional data. Please check with a PRBS checker the link quality. (https://www.xilinx.com/support/documentation/application_notes/xapp884_PRBS_GeneratorChecker.pdf)
From 0.8 to 0.9V (please see the UG) you can use the following configuration:
RXLPM_INCM_CFG = 1
RXLPM_IPCM_CFG = 0
RX_CM_TRIM [3:0] = 4’b1010 – 800 mV
RX_CM_TRIM [3:0] = 4’b1011 – 850 mV
RX_CM_TRIM [3:0] = 4’b1100 – 900 mV
RX_CM_SEL [1:0] = 2'b11
hope this helps
01-29-2018 09:37 AM
01-29-2018 07:02 PM - edited 01-29-2018 07:03 PM
This protocols are used for Panel Manufacturer to drive Source Driver IC (Such CHPI, CMPI, iSP, ...),
All of this protocols use DC Couple, but have different VCM (0.3V ~ 0.9V) and line rate (1.3Gbps ~ 3Gbps),
Those protocols need 100ohm termination resistor in RX side and have already described in standard spec,
I think "programmable mode" cannot be used, so I set RX_CM_SEL[1:0] = 2'b10 to use "float mode",
Unfortunately, RX_CM_TRIM[3:0] can not use in "float mode",
How GT know the current receiving VCM voltage, and choose suitable internal bias voltage in push-push mode configuration?
01-30-2018 08:14 AM
01-30-2018 11:47 AM - edited 01-30-2018 12:01 PM
hello,
The AC-coupling is recommended. If you must use the DC-coupling, please be careful with common mode currents. The receiver bias should match the signal common mode and the two ports
RXLPM_INCM_CFG
RXLPM_IPCM_CFG
are needed to enable the high/low common mode operation.
I do not find a characterization for common mode from 0.3V to <0.8V
At 0.3V I would try with
RXLPM_INCM_CFG = 0
RXLPM_IPCM_CFG = 1
RX_CM_TRIM [3:0] = 4’b0011 – 300 mV
RX_CM_SEL [1:0] = 2'b11
Because it is very close to Use mode 1 (table 4-3). Unfortunately I have no additional data. Please check with a PRBS checker the link quality. (https://www.xilinx.com/support/documentation/application_notes/xapp884_PRBS_GeneratorChecker.pdf)
From 0.8 to 0.9V (please see the UG) you can use the following configuration:
RXLPM_INCM_CFG = 1
RXLPM_IPCM_CFG = 0
RX_CM_TRIM [3:0] = 4’b1010 – 800 mV
RX_CM_TRIM [3:0] = 4’b1011 – 850 mV
RX_CM_TRIM [3:0] = 4’b1100 – 900 mV
RX_CM_SEL [1:0] = 2'b11
hope this helps
01-31-2018 01:18 AM