Altera RapidIO II MegaCore Function - Manual (Page 111)

Chapter 4: Functional Description 4–69
Logical Layer Interfaces
August 2014 Altera Corporation RapidIO II MegaCore Function
User Guide
Figure 4–26 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 4–26. Avalon-ST Pass-Through Interface SWRITE Receive Example
clk
gen_rx_hd_ready
gen_rx_hd_valid
0A0C600DD00AA00000AABBCC80000
FFFEFDFCFBFAF9F8F7F6F5F4F3F2F1F0 EFEEEDECEBEAE9E8E7E6E5E4E3E2E1E0
4
gen_rx_hd_data[114:0]
gen_rx_pd_valid
gen_rx_pd_ready
gen_rx_pd_startofpacket
gen_rx_pd_endofpacket
gen_rx_pd_data[127:0]
gen_rx_pd_empty[2:0]
Table 4–45. SWRITE 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’b11
tt[1:0] [101:100] 2’b00 Indicates 8-bit device IDs.
ftype[3:0] [99:96] 4’b0110
The value of 6 indicates a Streaming-Write Class
packet.