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Tool/software:
Hi, Dear supporter,
I am using DS80PCI402 to boost a 2x PCIe connection. If I using pin mode, set pin state as following, the EP device can be enumberated by host.
ENSMB |
1K to GND |
EQA[1:0] |
1K to GND, 1K to GND |
EQB[1:0] |
1K to GND, 1K to VIN |
DEMA[1:0] |
Float, Float |
DEMB[1:0] |
Float, Float |
LPBK |
Float |
VDD_SEL |
GND |
SD_TH |
Float |
/PRSNT |
LOW |
VIN |
3.3V |
Then I tied ENSMB to VIN to access the device from SMBUS, according to the table above, I set,
EQA0/1 = 0x00
EQB0/1 = 0x03
DEMA0/1 = 0x02
DEMB0/1 = 0x02
VOD = 0x05
However, the EP cannot be enumberated by host. Therefore,
1) Is there a way to read registers out by SMBUS when chip is in PIN mode? If yes, I can read the configuration out in PIN mode as a starting point for SMBUS mode.
2) I've provide the register dump and schematic as below, could you please help to analyze?
Data read from device:
0000: 40 00 00 00 00 00 10 01 00 00 cc 70 00 00 08 03
0010: ad a2 00 00 00 08 03 ad 82 00 00 00 00 2f ad 02
0020: 00 00 00 00 2f ad 02 00 0c 00 00 08 00 ad e2 00
0030: 00 00 08 00 ad e2 00 00 00 00 2f ad 02 00 00 00
0040: 00 2f ad 02 00 00 38 00 05 00 00 00 00 00 00 00
0050: 00 44 00 00 00 00 10 44 21 00 54 54 00 00 00 00
Hi Yong,
Your pin mode to register value conversion is correct.
Unfortunately it's not possible to access registers in pin mode.
I'll need some additional time to review your register dump and schematic. I'll get back to you with more feedback early next week.
Best,
Lucas
Hi, Lucas,
After re-check the datasheet, I forget to set bit 3 of register 0x06. After set it to 1, I can achieve similiar behavior as pin mode. I have another PCIe slot which is farther from CPU and PCIe card cannot be detected in this slot. As the distance increased, for EQ/VOD/DEM registers on host side, Should I increase/decrease each parameters to try?
Hi Yong,
I'm glad you were able to resolve the issue.
You will likely need to increase the EQ setting to support a longer channel. It's difficult to say how VOD and DEM need to be adjusted without manually tuning these parameters.
Do you have an estimate for insertion loss? This can serve as a good starting point to tune EQ.
Best,
Lucas