
EZ-USB FX2 Technical Reference Manual
Page 15-40 EZ-USB FX2 Technical Reference Manual v2.1
Example 2:
If you want the PF to inform the outside interface (the logic that is filling the IN FIFO) whenever the
current packet is 75% full, set PKTSTAT=1, and load a packet byte count of 75:
EP2FIFOPFH = 11xxx000
EP2FIFOPFHL = 75
Setting PKTSTAT=1 causes the PF decision to be based on the byte count alone, ignoring the
packet count. This mode is valuable for double-buffered endpoints, where only the byte count of
the currently-filling packet is important.
15.6.5.2 OUT Endpoints
For OUT endpoints, the PF flag applies to the total number of bytes in the multi-packet FIFO, with
no packet count field. Instead of representing byte counts in two segments, a packet count and a
byte count for the currently emptying packet, the byte Trigger values indicate total bytes available
in the FIFO. Note the discontinuity between PBC10 and PBC9.
Notice that the packet byte counts differ in the upper PBC bits because the endpoints support dif-
ferent FIFO sizes: The EP2 FIFO can be a maximum of 4096 bytes long, the EP6 FIFO can be a
maximum of 2048 bytes long, and the EP4 and EP8 FIFOS can be a maximum of 1024 bytes long.
The diagram below shows examples of the maximum FIFO sizes.
Figure 15-33. Maximum FIFO Sizes
512
512
512
512
EP2
EP4
512
512
512
512
EP2
512
512
512
512
EP6
EP8
512
512
512
512
EP6
512
512
512
512
EP2
512
512
EP6
1024
1024
EP2
1024
1024
EP6
1024
1024
EP2
1024
1024
1024
EP2
1024
1024
512
512
EP8
512
512
EP8
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