Intel
®
81341 and 81342—Application DMA Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
478
Order Number: 315037-002US
5.3.5
P+Q Update Descriptor Format
The P+Q Update descriptor can be used to perform a P+Q-Update-Transfer. To perform
a P+Q-Update-Transfer, the P+Q Update format descriptor must be written to local
shows the format of an individual P+Q Update chain
descriptor. Every P+Q Update descriptor requires 16 contiguous words in local memory
and is required to be aligned on a 32-byte address boundary. All 16 words are required.
Warning:
The hardware requires that bits 3 down to 0 of the Q_Destination Address (Word 2 and
5) and the P_Destination Address (Word 4 and 5) are programmed to the same four-bit
value. Furthermore, the hardware requires this even if the
P Transfer Disable
bit is
set to disable P transfer to the P_Destination Address. For example, in this case the
P_Destination Address may contain an invalid address such that bits 3 down to 0 of
that address equals to bits 3 down to 0 of the Q_Destination Address.
Figure 52. P+Q Update Descriptor Format
Next Descriptor Address
P - Destination Address (Lower)
P - Destination Address (Upper)
Descriptor Control
Reserved (00000000h)
Byte Count
Word 0
Word 2
Word 1
Word 3
Word 4
Word 5
Source 0 Address (Lower)
Source 0 Address (Upper)
Word 6
Word 7
Source 1 Address (Lower)
Source 1 Address (Upper)
Word 8
Word 9
P - Source Address (Lower)
P - Source Address (Upper)
Word 10
Word 11
Q - Source Address (Lower)
Q - Source Address (Upper)
Word 12
Word 13
Q - Destination Address (Lower)
Q - Destination Address (Upper)
Word 14
Word 15
DMLTQ
B6223-01