Table 22: TX and RX Power Control Signals
Bit Name
Value
Description
TXPWRDN_B
2’b11
Normal mode. Transceiver TX is actively sending data.
TXPWRDN_B
2’b00
Power-down mode. Transceiver TX is idle.
[RX_PDB_CH0, RX_PDB_CH1]
2’b11
Normal mode. Transceiver RX for channel 0 and channel 1 are
actively receiving data.
[RX_PDB_CH0, RX_PDB_CH1]
2’b00
Power-down mode. Transceiver RX for channel 0 and channel
1 are idle.
Loopback
Loopback modes are specialized configurations of the transceiver datapath where the traffic
stream is folded back to the source. Typically, a specific pattern is transmitted then compared to
check for errors. The following figure illustrates a loopback test configuration with three different
loopback modes.
Figure 21:
Loopback Testing Overview
`
RX-PMA
RX-PCS
TX-PMA
TX-PCS
RX-PCS
RX PMA
RX-PMA
TX-PCS
TX-PMA
Near-End GTM Transceiver
Far-End GTM Transceiver
Link Near-End Test Structures
Link Far-End Test Structures
Traffic
Checker
Traffic
Generator
Test Logic
1
2
3
X20907-061918
Loopback test modes fall into two broad categories:
• Near-end loopback modes loop transmit data back in the transceiver closest to the traffic
generator.
• Far-end loopback modes loop received data back in the transceiver at the far end of the data
link.
Loopback testing can be used either during development or in deployed equipment for fault
isolation. The traffic patterns used can be either application traffic patterns or specialized
pseudo-random bit sequences. Each GTM transceiver has a built-in PRBS generator and checker.
Chapter 2: Shared Features
UG581 (v1.0) January 4, 2019
Virtex Ult GTM Transceivers
46