Altera RapidIO II MegaCore Function User Manual
Page 101
Chapter 4: Functional Description
4–59
Logical Layer Interfaces
August 2014
Altera Corporation
RapidIO II MegaCore Function
User Guide
Figure 4–22
shows the behavior of the signals on the Avalon-ST pass-through
interface for this example transaction.
In the first clock cycle of the example, user logic asserts gen_rx_hd_ready and
gen_rx_pd_ready
, and the IP core asserts gen_rx_hd_valid and gen_rx_pd_valid,
indicating it is providing valid data on gen_rx_hd_data and gen_rx_pd_data,
respectively. The assertion of both the ready signal and the valid signal on each of the
header and payload-data Avalon-ST interfaces makes the current cycle an Avalon-ST
ready cycle for both header and data.
The IP core asserts gen_rx_pd_startofpacket to indicate the current cycle is the first
valid data cycle of the packet. In this clock cycle, the IP core also makes the header
and the first 128 bits of payload data available on gen_rx_hd_data and
gen_rx_pd_data
, respectively. The 40-byte payload requires 3 clock cycles. In the third
clock cycle of data transfer, the IP core asserts gen_rx_pd_endofpacket to indicate this
is the final clock cycle of data transfer, and specifies in gen_rx_pd_empty that in the
current clock cycle, the four least significant two-byte segments (the least significant
eight bytes) of gen_rx_pd_data are not valid. Following the clock cycles in which valid
data is available on gen_rx_pd_data, the IP core deasserts gen_rx_pd_valid.
Table 4–35
lists the header fields in this example.
Figure 4–22. Avalon-ST Pass-Through Interface NWRITE Receive Example
clk
gen_rx_hd_ready
gen_rx_hd_valid
000102030405060708090A0B0C0D0E0F
101112131415161718191A1B1C1D1E1F
20212223242526270000000000000000
4
0A00500DD00AA4C00FEDCBA940000
gen_rx_hd_data[114:0]
gen_rx_pd_ready
gen_rx_pd_valid
gen_rx_pd_startofpacket
gen_rx_pd_endofpacket
gen_rx_pd_data[127:0]
gen_rx_pd_empty[2:0]
Table 4–35. NWRITE Request Receive Example: RapidIO Header Fields in gen_rx_hd_data Bus (Part 1 of 2)
Field
gen_rx_hd_data
Bits
Value
Comment
pd_size[8:0]
[114:106]
9’h028
Payload data size is 0x28 (decimal 40).
VC
[105]
0
The RapidIO II IP core supports only VC0.
CRF
[104]
0
prio[1:0]
[103:102]
2’b00
tt[1:0]
[101:100]
2’b00
Indicates 8-bit device IDs.
ftype[3:0]
[99:96]
4’b0101
The value of 5 indicates a Write Class packet.
destinationID[15:0]
[95:80]
16’h00DD
For variations with an 8-bit device ID, bits [95:88] (bits
[15:8] of the destinationID) are set to 8’h00.