Altera IP Compiler for PCI Express - Manual (Page 92)

5–6 Chapter 5: IP Core Interfaces
Avalon-ST Interface
IP Compiler for PCI Express User Guide August 2014 Altera Corporation
64- or 128-Bit Avalon-ST RX Port
Table 5–2 describes the signals that comprise the Avalon-ST RX Datapath.
Table 5–2. 64- or 128-Bit Avalon-ST RX Datapath (Part 1 of 3)
Signal Width Dir
Avalon-ST
Type
Description
rx_st_ready <n> (1) (2) 1 I ready
Indicates that the application is ready to accept data. The
application deasserts this signal to throttle the data stream.
rx_st_valid<n> (2) 1 O valid
Clocks rx_st_data<n> into application. Deasserts within 3
clocks of rx_st_ready<n> deassertion and reasserts within 3
clocks of rx_st_ready<n> assertion if more data is available
to send. rx_st_valid can be deasserted between the
rx_st_sop
and rx_st_eop even if rx_st_ready is asserted.
rx_st_data<n>
64,
128
O data
Receive data bus. Refer to Figure 5–5 through Figure 5–13 for
the mapping of the transaction layer’s TLP information to
rx_st_data
. Refer to Figure 5–15 for the timing. Note that the
position of the first payload dword depends on whether the TLP
address is qword aligned. The mapping of message TLPs is the
same as the mapping of transaction layer TLPs with 4 dword
headers. When using a 64-bit Avalon-ST bus, the width of
rx_st_data<n>
is 64. When using a 128-bit Avalon-ST bus,
the width of rx_st_data<n> is 128.
rx_st_sop<n> 1 O
start of
packet
When asserted with rx_st_valid<n>, indicates that this is the
first cycle of the TLP.
rx_st_eop<n> 1 O
end of
packet
When asserted with rx_st_valid<n>, indicates that this is the
final cycle of the TLP.
rx_st_empty<n> 1 O empty
Indicates that the TLP ends in the lower 64 bits of rx_st_data.
Valid only when rx_st_eop<n> is asserted. This signal only
applies to 128-bit mode in the hard IP implementation.
When rx_st_eop<n> is asserted and rx_st_empty<n> has
value 1, rx_st_data[63:0] holds valid data but
rx_st_data[127:64]
does not hold valid data.
When rx_st_eop<n> is asserted and rx_st_empty<n> has
value 0, rx_st_data[127:0] holds valid data.