DS471 Datasheet, PDF (33/37 Pages) Xilinx, Inc – Channel FIFO

Channel FIFO (CFIFO) (v1.00a)
Figure Top x-ref 24
Clk
Rst
Bus2WFIFO_Ch_Num[0:7] 02
Bus2WFIFO_Burst
Bus2WFIFO_Data_WrReq
Bus2WFIFO_Status_RdReq
WFIFO2Bus_Ack
WFIFO2Bus_ErrAck
WFIFO2Bus_Ch_Valid
Bus2WFIFO_DBus[0:31]
Bus2WFIFO_Tag[0:3]
WFIFO2Bus_Status[0:31]
Comm2WFIFO_Ch_Num[0:7]
WFIFO2Comm_Ch_Valid
Comm2WFIFO_Burst
Comm2WFIFO_RdReq
WFIFO2Comm_Ack
WFIFO2Comm_ErrAck
WFIFO2Comm_DBus[0:31]
WFIFO2Comm_Tag[0:3]
WFIFO2Comm_HalfEmpty
WFIFO2Comm_AlmostEmpty
WFIFO2Comm_Empty
WFIFO2Comm_Occupancy[0]:7
cycle 1
01
05
FFEE BBA 7766 3322
DDCC A9988 5544 1100
0
2
0000
00FE
0000
00FB
03
01
0000
00FF
3333
3333
1
FFEE BBAA
DDCC 9988
0
7766
5544
3322
1100
2
01
00
04
03 02 01
00
2 3 4 5 6 7 8 9 10 11 12 13 14 15
Figure 24: WFIFO Context Switch During Burst
DS471_24_101405
WFIFO Tag Field
The tag field associated with each data location in the WFIFO is intended to be used for marking an
end-of-packet location within a channel, as well as distinguishing which byte within that location
contains the last byte of the packet. A tag field is not needed in the RFIFO because the end-of-packet
information is handled differently when receiving data.
From the viewpoint of the WFIFO, the tag field is just an additional k bits of information to be stored
along with its associated data and retrieved when the data is read, where k is equal to C_DWIDTH/8.
Figure 25 shows the WFIFO tag field.
Figure Top x-ref 25
0
k-1
MSB
LSB
DS471_24_101405
Figure 25: WFIFO Tag Field
DS471 April 24, 2009
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33
Product Specification