Motorola MPC823e - Page 554

Communication Processor Module
16-100 MPC823e REFERENCEMANUAL MOTOROLA
IDMA
COMMUNICATION
16
PROCESSOR MODULE
SOURCE BUFFER POINTER
This field contains the address of the associated source data buffer and can reside in
internal or external memory.
DESTINATION BUFFER POINTER
This field contains the address of the associated destination data buffer, which resides in
internal or external memory.
The terminal count code AT = 0xF replaces the normal SFCR and DFCR code for the last
IDMA cycle on the peripheral side.
16.6.3.6 IDMA COMMANDS. There are three IDMA commands:
• INIT_IDMA—This command causes the RISC microcontroller to reinstall its IDMA
internal state to the condition it was in after a system reset. The IDMA buffer descriptor
pointer is reinitialized to the top of the buffer descriptor ring.
• ARM_IDMA—This command causes the IDMA to open the next buffer descriptor in the
table. It can be used to reduce the latency of servicing the first IDMA request.
• STOP_IDMA—This command causes the RISC microcontroller to terminate current
IDMA transfers. The DONE bit is set in the IDSRx and the current buffer descriptor is
closed. If the peripheral device is the source, the IDMA internal buffer is transferred to
memory before termination. At the next request, the following buffer descriptor in the
chain is processed.
Note: In single address mode when the source is a device, the SOURCE BUFFER
POINTER field is ignored. In dual address mode when the source is a device,
this field must contain the device address.
Note: In single address mode when the destination is a device, the DESTINATION
BUFFER POINTER field is ignored. In dual address mode when the destination
is a device, this field must contain the device address.