Table of Contents
Advertisement
Communication Processor Module
16.6.3.5 IDMA BUFFER DESCRIPTORS. The special IDMA buffer descriptors present the
source addresses, destination addresses, and byte counts to the RISC microcontroller. The
RISC microcontroller reads the buffer descriptors, programs the SDMA channel, and notifies
the core about the completion of a buffer transfer using the IDMA buffer descriptors. This
process is similar to that of the serial channels, except that the buffer descriptor is larger
because it contains additional information.
0
1
2
V
RES
W
OFFSET + 0
OFFSET + 2
OFFSET + 4
OFFSET + 6
OFFSET + 8
OFFSET + A
OFFSET + C
OFFSET + E
NOTE: You are only responsible for initializing the items in bold.
You must prepare the following bits before a transfer can occur. They are set by the RISC
microcontroller after the buffer has been transferred.
V—Valid
0 = The data buffers associated with this buffer descriptor are not currently ready for
transfer. You are free to manipulate this buffer descriptor or its associated data
buffer. When it is not in autobuffer mode, the RISC microcontroller clears this bit
after the buffer has been transferred (or after an error condition is encountered).
1 = You have prepared the data buffers for transfer. Notice that only one data buffer
must be prepared if the source/destination is a peripheral device. It can only be the
source data buffer when the destination is a device or the destination data buffer
when the source is a device. You can not write any fields of this buffer descriptor
once this bit is set.
Note: The only difference between autobuffer mode and buffer-chaining mode is that
the V bit is not cleared by the RISC microcontroller in autobuffer mode.
Autobuffer mode is enabled by the CM bit.
16-96
3
4
5
6
7
I
L
RES
CM
DFCR
DATA LENGTH
SOURCE DATA BUFFER POINTER
DESTINATION DATA BUFFER POINTER
MPC823e REFERENCEMANUAL
8
9
10
11
12
RESERVED
SFCR
13
14
15
MOTOROLA
Advertisement
Table of Contents
