UP4000 PCIe Connections
I am trying to set up a PCIe connection to the UP4000 board through CN21. Typically in PCIe comms you have a CWAKE# signal and a CPWRON signal. CWAKE# is pulled high from the standby power to indicate the card is wake capable. CPWRON indicates that the supply voltage rails have achieved a minimum nominal value.
Is CWAKE# used on the up4000 board? Is this the PCIe_WAKE_1V8 signal on the datasheet and is it pulled up on the UP4000 board or do I need to pull it up externally?
Is CPWRON used on the UP4000 board and if so, which signal on CN21 would this connect to?
My reference for these signals is: https://en.wikipedia.org/wiki/PCI_Express.
Thanks in advance for any support.
Answers
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Hi @TB1
CWAKE and PCIe_WAKE_1V8 are the same and it is connected to the CPU on the mainboard.
A 4.7K pull-up resistor is already present on the mainboard, so please do not connect it to any other power source.There is no CPWRON signal on CN21, but there is a similar signal available for use. BUF_PLT_RST# (Pin28) can be used instead.
This signal is the CPU's platform reset signal, and when "all power" conditions are met, the CPU will pull this signal to a high level. In this circuit design, it operates at 3.3V.
Additionally, since this signal is directly connected from the CPU, it is recommended to add a buffer in the board redesign to enhance the driving capability.Best Regards,
Harry Chiu