6–22
Chapter 6: IP Core Interfaces
Avalon-ST TX Interface
Arria V GZ Hard IP for PCI Express
November 2012
Altera Corporation
illustrates the mapping between Avalon-ST TX packets and PCI Express
TLPs for four dword header with non-qword aligned addresses with a 64-bit bus.
illustrates the timing of the TX interface when the Arria V GZ Hard IP for
PCI Express backpressures the Application Layer by deasserting
tx_st_ready
.
Because the
readyLatency
is two cycles, the Application Layer deasserts
tx_st_valid
after two cycles and holds
tx_st_data
until two cycles after
tx_st_ready
is asserted.
illustrates back-to-back transmission of 64-bit packets with no idle cycles
between the assertion of
tx_st_eop
and
tx_st_sop
.
Figure 6–21. 64-Bit Avalon-ST tx_st_data Cycle Definition for TLP 4-Dword Header with Non-Qword Aligned Address
pld_clk
tx_st_data[63:32]
tx_st_data[31:0]
tx_st_sop
tx_st_eop
Header 1
Header3
Data0
Data2
Header 0
Header2
Data1
Figure 6–22. 64-Bit Transaction Layer Backpressures the Application Layer
tx_st_sop
tx_st_eop
tx_st_ready
tx_st_valid
tx_st_err
tx_st_data[63:0]
.
.
.
.
.
.
.
.
.
.
readyLatency
00. .
00 ...
BB...
BB ... BBBB0306BBB0305 BB...
BB..
BB ... BB ...
BB ... BB ... BB....
Figure 6–23. 64-Bit Back-to-Back Transmission on the TX Interface
coreclkout
tx_st_sop
tx_st_eop
tx_st_ready
tx_st_valid
tx_st_err
tx_st_data[63:0]
01 ... 00 ... BB ... BB ... BB ... BB ... B ...
... BB ... 01 ... 00 ... CC ... CC ... CC ...
CC ... CC ... CC ...