Altera Corporation
2–157
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Receiver Status
The PIPE interface for PCI Express has a receiver status indicator that
reports the status of the PHY (PCS and PMA). The receiver status is
communicated to the PLD logic by the 3-bit
pipestatus
port. This port
enumerates the status as shown in
Table 2–36
. If more than one event
occurs at the same time, the signal is resolved with the higher priority
status.The skip character added and removed flags (3'b001 and 3'b010)
are not supported. The
pipestatus
port may be encoded to 3b'001 and
3'b010, which should be ignored. It does not indicate that a skip has been
added or removed and should be considered the same as 3'b000—
received data. If the upper MAC layer must know when a skip character
was added or removed, Altera recommends monitoring the number of
skip characters received. The transmitter should send three skip
characters in a standard skip-ordered set.
Table 2–35. Power States and Functions Allowed in Each Power State
Power State
tx_detectrxloopback
tx_forceelecidle
P0
0: normal mode
1: data path in loopback mode
0: Must be deasserted.
1: Illegal mode
P0s
Don’t care
0: Illegal mode
1: Must be asserted in this state
P1
0: Electrical Idle
1: receiver detect
0: Illegal mode
1: Must be asserted in this state
P2
Don’t care
Deasserted in this state for
sending beacon.
Otherwise asserted.
Table 2–36. pipestatus Description and Priority
pipestatus
Description
Priority
3’b000
Received data
6
3’b001
One skip character added (not supported)
N/A
3’b010
One skip character removed (not supported)
N/A
3’b011
Receiver detected
1
3’b100
8B/10B decoder error
2
3’b101
Elastic buffer overflow
3
3’b110
Elastic buffer underflow
4
3’b111
Received disparity error
5