Altera RapidIO MegaCore Function User Manual
Page 106
4–60
Chapter 4: Functional Description
Logical Layer Modules
RapidIO MegaCore Function
August 2014
Altera Corporation
User Guide
shows a response to a 32-byte NREAD request in a RapidIO IP core with
16-bit device ID.
shows the composition of the fields in the RapidIO packet
header and the payload as they correspond to each clock cycle. The gen_tx_empty bits
indicate a value of 0, because all bytes of the last word are read.
Table 4–16. RapidIO Header Fields on the gen_tx_data Bus (Part 1 of 2)
Cycle
Field
gen_tx_data bus
Value
Comment
1
ackID
[63:59]
5'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.
rsvd
[58:57]
2'h0
CRF
[56]
1'b0
prio
[55:54]
2'b10
Priority of the RESPONSE packet. Value must be
incremented from the priority value of the REQUEST
packet. For example, prio value 2’b10 indicates that the
original request had a priority value of 2’b01.
tt
[53:52]
2'h1
Indicates 16-bit device IDs.
ftype
[51:48]
4'hd
A value of 4'hd (13 decimal) indicates a Response Class
packet.
destinationId
[47:32]
16'hccdc
In the case of a RapidIO IP core variation with a 8-bit
device ID width, the destinationID and sourceID fields
shrink to a width of 8 bits each, and the fields described
in the following table rows shift to the left and to an
earlier clock cycle if appropriate.
sourceId
[31:16]
16'haaba
ttype
[15:12]
4'h8
A value of 8 indicates a RESPONSE transaction with data
payload.
status
[11:8]
4'h0
A value of 0 indicates DONE. Requested transaction has
been successfully completed.
targetTID
[7:0]
8'h00
Value in the response packet matches the sourceTID of
the corresponding request packet.
2
Payload Byte0,1
[63:48]
16'h0102
Payload double word 0
Payload Byte2,3
[47:32]
16'h0304
Payload Byte4,5
[31:16]
16'h0506
Payload Byte6,7
[15:0]
16'h0708
3
Payload Byte8,9
[63:48]
16'h090a
Payload double word 1
Payload
Byte10,11
[47:32]
16'h0b0c
Payload
Byte12,13
[31:16]
16'h0d0e
Payload
Byte14,15
[15:0]
16'h0f10