FX3 Programmers Manual, Doc. # 001-64707 Rev. *C
145
FX3 P-Port Register Access
The AP may abort a transfer in the middle of a burst or at the end of a burst. Note that it is not pos-
sible to implement a transfer of a non-integral number of bursts using the AP abort mechanism. This
requires the adjustment of the DMA_SIZE register as illustrated in the next section.
10.4.7
Long Transfer – Partial Last Buffer on Ingress
When a long ingress transfer has a partial last buffer, this buffer can be preceded by an adjustment
by AP of DMA_SIZE. If no such adjustment is made and the transfer is shorter than the coordinated
transfer size (that is set into the DMA Adapter’s trans_size by firmware), it is possible to exchange
whole words/bursts only.
The following diagram illustrates this concept:
Figure 10-9. Ingress Long Transfer with a Partial Last Buffer
The following should be noted:
Before transferring the last buffer, the AP adjusts DMA_SIZE. AP must assure that DMA_READY=1
or DMA_WMARK=1 before writing to DMA_SIZE. This can be done using the signals directly (e.g.
through INTR/DRQ signaling) or by explicitly polling for DMA_SIZE.VALID=1.
If no adjustment of DMA_SIZE is made, but the long transfer itself was indicated to have a non-inte-
gral number of bursts, the DMA Adapter will truncate any data written by AP beyond the end of the
transfer. In other words, this mechanism is not required and AP may terminate the transfer after writ-
ing the last full burst.
10.4.8
Long Transfer – Partial Last Buffer on Egress
On egress, a partial last buffer results in early de-assertion of DMA_WMARK but is otherwise no dif-
ferent from a transfer of a whole number of buffers. The following diagram illustrates this:
DMA_READY
SOCK_STAT[N]
A/D
R/W#
DMA_
XFER
DMA_ENABLE
DMA_WMARK
N
2
DMA_
XFER
Buffer 0
Burst 1
Buffer 0
Burst 0
Buffer 0
Burst 3
Buffer 0
Burst 2
Buffer N
Burst 1
Buffer N
Burst 0
0
DMA_
SIZE
Summary of Contents for EX-USB FX3
Page 8: ...8 FX3 Programmers Manual Doc 001 64707 Rev C Contents...
Page 12: ...12 FX3 Programmers Manual Doc 001 64707 Rev C Introduction...
Page 48: ...48 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Overview...
Page 74: ...74 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Firmware...
Page 76: ...76 FX3 Programmers Manual Doc 001 64707 Rev C FX3 APIs...
Page 84: ...84 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Application Examples...
Page 98: ...98 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Application Structure...
Page 148: ...148 FX3 Programmers Manual Doc 001 64707 Rev C FX3 P Port Register Access...
Page 165: ...FX3 Programmers Manual Doc 001 64707 Rev C 165 FX3 Development Tools Click next...
Page 178: ...178 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Development Tools Click on Apply...
Page 180: ...180 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Development Tools d Start the GDB server...
Page 185: ...FX3 Programmers Manual Doc 001 64707 Rev C 185 FX3 Development Tools...
Page 186: ...186 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Development Tools...
Page 187: ...FX3 Programmers Manual Doc 001 64707 Rev C 187 FX3 Development Tools...
Page 188: ...188 FX3 Programmers Manual Doc 001 64707 Rev C FX3 Development Tools...
Page 192: ...192 FX3 Programmers Manual Doc 001 64707 Rev C GPIF II Designer...
