User guide

Figure 2-80: Speed Change Sequence
pipe_tx_elecidle
pipe_rate[1:0]
pipe_sw[1:0]
pipe_sw_done[1:0]
pipe_phy_status
00 10
00
00
10
10
Gen3 Transmitter Electrical Idle Generation
In the PIPE 3.0-based interface, you can place the transmitter in electrical idle during low power states.
Before the transmitter enters electrical idle, you must send the Electrical Idle ordered set, consisting of 16
symbols with value 0x66. During electrical idle, the transmitter differential and common mode voltage
levels are based on the PCIe Base Specification 3.0.
Gen3 Clock Compensation
Enable this mode from the Parameter Editor when using the Gen3 PIPE transceiver configuration rule.
To accommodate PCIe protocol requirements and to compensate for clock frequency differences of up to
±300 ppm between source and termination equipment, receiver channels have a rate match FIFO. The
rate match FIFO adds or deletes four SKP characters (32 bits) to keep the FIFO from becoming empty or
full. If the rate match FIFO is almost full, the FIFO deletes four SKP characters. If the rate match FIFO is
nearly empty, the FIFO inserts a SKP character at the start of the next available SKP ordered set. The
pipe_rx_status [2:0] signal indicates FIFO full, empty, insertion and deletion.
Note:
Refer to the Gen1 and Gen2 Clock Compensation section for waveforms.
Related Information
Gen1 and Gen2 Clock Compensation on page 2-232
Gen3 Power State Management
The PCIe base specification defines low power states for PHY layer devices to minimize power consump‐
tion. The Gen3 PCS does not implement these power saving measures, except when placing the
transmitter driver in electrical idle in the low power state. In the P2 low power state, the transceivers do
not disable the PIPE block clock.
Figure 2-81: P1 to P0 Transition
The figure below shows the transition from P1 to P0 with completion provided by pipe_phy_status.
P1 P0
tx_coreclkin
pipe_powerdown
pipe_phy_status
UG-01143
2015.05.11
Gen3 Transmitter Electrical Idle Generation
2-237
Implementing Protocols in Arria 10 Transceivers
Altera Corporation
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