P/N Polarity

In a SERDES link, you transmit data at high speeds over differential pairs. Each pair has two signals:

• P (positive)

• N (negative)

Normally, the transmitter sends the differential signal correctly: when the P is high, N is low, and vice versa. However, in real hardware, especially during PCB design or cable assembly, sometimes the P and N wires get accidentally swapped.

You can enable the P/N polarity swap of a SERDES in PMA tab in XenaManager, as shown in the screenshot below. By default, the RX and TX P/N polarity swap is off.

P/N Polarity Swap TX

Corresponding low-level API class: PL1_PNSWAP_TX

await port.l1.serdes[0].pma.pn_swap_tx.set(on_off=enums.OnOff.ON)
await port.l1.serdes[0].pma.pn_swap_tx.set_on()
await port.l1.serdes[0].pma.pn_swap_tx.set(on_off=enums.OnOff.OFF)
await port.l1.serdes[0].pma.pn_swap_tx.set_off()

resp = await port.l1.serdes[0].pma.pn_swap_tx.get()
resp.on_off

P/N Polarity Swap RX

Corresponding low-level API class: PL1_PNSWAP_RX

await port.l1.serdes[0].pma.pn_swap_rx.set(on_off=enums.OnOff.ON)
await port.l1.serdes[0].pma.pn_swap_rx.set_on()
await port.l1.serdes[0].pma.pn_swap_rx.set(on_off=enums.OnOff.OFF)
await port.l1.serdes[0].pma.pn_swap_rx.set_off()

resp = await port.l1.serdes[0].pma.pn_swap_rx.get()
resp.on_off