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PCM-072/phyCORE-AM64xx System on Module
L-860e.A0
© PHYTEC America L.L.C. 2022
64
7.5.1 PCIe Pinout
Table 32 PCIe Connections at the phyCORE-Connector
X1 Pin #(s)
SOM Signal(s)
Type
Level
Description
A25
X_SERDES0_TX0_N
O
Differential
PCIe Transmit Data 0 Negative
A24
X_SERDES0_TX0_P
O
Differential
PCIe Transmit Data 0 Positive
A28
X_SERDES0_RX0_N
I
Differential
PCIe Receive Data 0 Negative
A27
X_SERDES0_RX0_P
I
Differential
PCIe Receive Data 0 Positive
A21
X_SERDES0_REFCLK0_P
(49.9 pulldown)
I/O
Differential
PCIe Reference Clock Positive
A22
X_SERDES0_REFCLK0_N
(49.9 pulldown)
I/O
Differential
PCIe Reference Clock Negative
B20
X_PCIE_CHIP_CLKREQ_B
I
3.3V
1
PCIe Clock Request
1
:
The voltage level for this signal is configurable for 1.8V or 3.3V via J5. The default voltage level is listed here, but always check the actual jumper setting for the
applicable SOM configuration. Refer to section
for details
7.5.2 PCIe (SERDES) Design In Considerations
•
The PCIe subsystem allows for up to 1x single-lane PCIe port.
•
An external clock is required to drive the PCIe reference clock inputs, X_SERDES0_REFCLK0_P/
X_SERDES0_REFCLK0_N. The external clock must be a high-quality, low-jitter differential 100MHz clock source
compliant to the PCIe REFCLK AC specifications. We recommend using the PI6C557-03 clock generator, which is
implemented on the PHYTEC carrier board. A PCIe reference circuit is shown in section
•
AC coupling capacitors for PCIe transmit signals are implemented on the SOM.
Table 33 phyCORE-AM64xx SERDES0 Layout Characteristics
Signal Name
Length (µm)
Length
Matching
(µm)
Single Ended
Impedance (Ω)
Differential
Impedance (Ω)
SOM
Trace
Max Total
Max CB
Trace
X_SERDES0_TX0_N
4692
101600
96908
127
50
100
X_SERDES0_TX0_P
4680
101600
96920
50
X_SERDES0_RX0_N
6159
101600
95441
127
50
100
X_SERDES0_RX0_P
6160
101600
95440
50
7.5.3 PCIe Reference Circuits
An example reference circuit for connecting the SERDES differential signals to a mini-PCIe connector and a PCIe clock
generator are shown below.