Achronix Speedster22i PCIe - Manual (Page 28)

UG030, April 26, 2013 28
Port Name Direction Clock Description
User’s task: User logic must stop the
transmission of new Non-Posted requests
when vc0_tx_np_ok == 0. A non-posted packet
transmission that has already asserted
vc0_tx_sop must continue to be transmitted in
full. vc0_tx_np_ok should be used to stop new
assertions of vc0_tx_sop for non-posted
requests. Because vc0_tx_np_ok is an almost
full flag, it is allowed for vc0_tx_np_ok to be
used as the input to the register that generates
vc0_tx_sop for non-posted transactions
(vc0_tx_np_ok does not have to be used
combinatorial to mask vc0_tx_sop).
It is recommended for all user designs to use
vc0_tx_np_ok.
bypass_rx_valid Output bypass_clk DMA Bypass Rx Data Valid
bypass_rx_ready Input bypass_clk DMA Bypass Rx Ready
bypass_rx_data[127:0] Output bypass_clk TLP data to receive; vc0_rx_data is valid from
the assertion of vc0_rx_sop until the packet is
fully consumed with the assertion of
vc0_rx_eop == vc0_rx_en == 1.
TLP data comprises a complete Transaction
Layer packet as defined by the PCI Express
Specification including the entire packet
header, data payload, and optional TLP Digest
(ECRC). The core strips the packet’s
STP/END/EDB framing, Sequence Number,
and Link CRC as part of its Data Link Layer
functionality prior to the TLP appearing on
this interface. The core checks TLP ECRC,
when present and when checking is enabled,
but does not remove the ECRC from the TLP.
PCI Express TLPs are integer multiples of 32-
bits in length. Thus, 64-bit and 128-bit Core
Data Width cores may have an unused
remainder portion in the final data word of a
packet. The user is responsible for detecting
and discarding any unused remainder at the
end of the TLP. All of the necessary
information to detect a remainder is located in
the packet TLP header (Length, TLP Digest,
and Format and Type) fields.
bypass_rx_data_valid[15:0] Output bypass_clk DMA Bypass Rx Data Byte Valid
bypass_rx_sop Output bypass_clk Start of TLP indicator and packet receive
request; set == 1 coincident with the first
vc0_rx_data word in each TLP. Once