Altera RapidIO II MegaCore Function User Manual
Page 92
4–50
Chapter 4: Functional Description
Logical Layer Interfaces
RapidIO II MegaCore Function
August 2014
Altera Corporation
User Guide
Table 4–25
list the required format of the TX header information on the
gen_tx_data
bus for both device ID widths. The required format derives directly from
the RapidIO specification. You must include the header information in the clock cycle
in which you assert gen_tx_startofpacket. Note that the ackID field is filled by the IP
core, and the eight-bit device ID fields are not extended with zeroes, in contrast to the
destinationID and source ID fields in gen_rx_hd_data.
gen_tx_startofpacket
Input
Marks the active cycle containing the start of the packet. The user logic asserts
gen_tx_startofpacket
and gen_tx_valid to indicate that a packet is
available for the IP core to sample.
(1)
gen_tx_endofpacket
Input
Marks the active cycle containing the end of the packet.
(1)
gen_tx_data[127:0]
Input
A 128-bit wide data bus. Carries the bulk of the information transferred from the
source to the sink.
(1)
The RapidIO II IP core fills in the RapidIO packet ackID field and adds the CRC
bits and padding bytes, but otherwise copies the bits from gen_tx_data to the
RapidIO packet without modifying them. Therefore, you must pack the
appropriate RapidIO packet fields in the correct RapidIO packet format in the
most significant bits of the gen_tx_data bus, gen_tx_data[127:N]. The
total width (127 – N + 1) of the header fields depends on the transaction and the
device ID width, as shown in
, and in
Interface Usage Examples” on page 4–56
gen_tx_empty[3:0]
Input
This bus identifies the number of empty bytes on the final data transfer of the
packet, which occurs during the clock cycle when gen_tx_endofpacket is
asserted.
(1)
The number of empty bytes must always be even.
gen_tx_packet_size[8:0]
Input
Indicates the number of valid bytes in the packet being transferred. The IP core
samples this signal only while gen_tx_startofpacket is asserted. User logic
must ensure this signal is correct while gen_tx_startofpacket is asserted.
:
(1) gen_tx_valid is used to qualify all the other input signals of the transmit side of the Avalon-ST pass-through interface.
(2) This signal is not defined in th
. However, it refers to data being transferred on the Avalon-ST sink interface.
Table 4–24. Avalon-ST Pass-Through Interface Transmit Side (Avalon-ST Sink) Signals (Part 2 of 2)
Signal Name
Type
Function
Table 4–25. RapidIO Header Information Format on gen_tx_data Bus
Field
gen_tx_data Bits
Device ID Width 8
Device ID Width 16
ackID[5:0]
[127:122]
[127:122]
VC
[121]
[121]
CRF
[120]
[120]
prio[1:0]
[119:118]
[119:118]
tt[1:0]
[117:116]
[117:116]
ftype[3:0]
[115:112]
[115:112]
destinationID[<deviceIDwidth>–1:0]
[111:104]
[111:96]
sourceID[<deviceIDwidth>–1:0]
[103:96]
[95:80]
specific_header
[95:...]
[79:...]