Avalon-st interface data transfer timing, Packet data transfers, Avalon-st interface data transfer timing -12 – Altera CIC MegaCore Function User Manual
Page 28: Packet data transfers -12
Signal
Directio
n
Description
out_endofpacket
Output Marks the end of the outgoing result group. If '1', a result
corresponding to channel N-1 is output, where N is the number of
channels.
out_error
Output Error signal indicating Avalon-ST protocol violations on source
side:
• 00: No error
• 01: Missing start of packet
• 10: Missing end of packet
• 11: Unexpected end of packet
Other types of errors may also be marked as 11.
out_ready
Input
Asserted by the downstream module if it is able to accept data.
out_startof-
packet
Output Marks the start of the outgoing result group. If '1', a result
corresponding to channel 0 is output.
out_valid
Output Asserted by the IP core when there is valid data to output.
rate
Input
This signal is available when the variable rate change factor option
is enabled. You can use it to change the decimation or interpola‐
tion rate during run time. It has the size Ceil(log
2
(maximum rate))
.
Avalon-ST Interface Data Transfer Timing
Figure 3-7: Avalon-ST Interface Timing with READY_LATENCY=0
D
o
D
1
D
2
0
1
2
3
5
6
7
8
4
clk
ready
valid
error
data
00
00
00
00
D
2
The source provides data and asserts
valid
on cycle 1, even though the sink is not ready. The source waits
until cycle 2, when the sink does assert
ready
, before moving onto the next data cycle. In cycle 3, the
source drives data on the same cycle and because the sink is ready to receive it, the transfer occurs
immediately. In cycle 4, the sink asserts
ready
, but the source does not drive valid data.
Packet Data Transfers
A beat is the transfer of one unit of data between a source and sink interface. This unit of data may consist
of one or more symbols and makes it is possible to support modules that convey more than one piece of
information about each valid cycle.
Packet data transfers are used for multichannel transfers. Two additional signals (
startofpacket
and
endofpacket
) are defined to implement the packet transfer.
3-12
Avalon-ST Interface Data Transfer Timing
UG-CIC
2014.12.15
Altera Corporation
CIC IP Core Functional Description