Altera RapidIO II MegaCore Function - Manual (Page 108)

4–66 Chapter 4: Functional Description
Logical Layer Interfaces
RapidIO II MegaCore Function August 2014 Altera Corporation
User Guide
The initial eight bytes of the NREAD response packet contain header information.
Table 4–41 lists the header fields and their values in this example.
User Sending Streaming Write Request
Table 4–42 lists the Avalon-ST pass-through interface usage example this section
describes.
Table 4–41. NREAD Response Transmit Example: RapidIO Header Fields on the gen_tx_data Bus
Field
gen_tx_data
Bits
Value Comment
ackID [127:122] 6'h00
Value is a don’t care, because it is overwritten by the Physical
layer ackID value before the packet is transmitted on the
RapidIO link.
VC [121] 0 The RapidIO II IP core supports only VC0.
CRF [120] 0
prio[1:0] [119:118] 2'b10
Priority of the response packet. Value must be higher than the
priority value of the request packet. In this example, the
response packet has a priority value of 2’b10 and the original
request has a priority value of 2’b01.
tt[1:0] [117:116] 2'b01 The value of 1 indicates 16-bit device IDs.
ftype[3:0] [115:112] 4’b1101
The value of 4’hD (decimal 13) indicates a Response Class
packet.
destinationId[15:0] [111:96] 16’hAAAA The sourceID and destinationID of the NREAD request are
swapped in the response transaction.
sourceId[15:0] [95:80] 16’hDDDD
ttype[3:0] [79:76] 4’b1000
The value of 8 indicates a Response transaction with data
payload.
status[3:0] [75:72] 4’b0000
The value of 0 indicates Done. The current packet successfully
completes the requested transaction.
transactionID[7:0] [71:64] 8'hBB
Value in the response packet matches the transactionID of
the corresponding request packet.
Table 4–42. Avalon-ST Pass-Through Interface Usage Example: Send SWRITE Request
User Operation
Operation
Type
RapidIO Transaction Priority
Device ID
Width
Payload Size
(Bytes)
Send streaming write request Tx SWRITE 3 8 40