Motorola MPC823e Reference Manual page 537

Communication Processor Module
Each SDMA channel can be programmed to output one of eight function codes that identify
the channel currently accessing memory. The SDMA channel can be assigned a big-endian
(Motorola) or little-endian format for accessing buffer data. These features are programmed
in the receive and transmit function code registers that are associated with the serial
communication controllers, serial management controllers, serial peripheral interface, and
2
I C controller. If a bus error occurs when the SDMA conducts a RISC-related access, the
communication processor module generates a unique interrupt in the RISC status register.
The interrupt service routine reads the SDMA address register to determine the address that
the bus error occurred on. The channel that caused the bus error can be found by reading
the receive and transmit internal data pointers from the specific protocol parameters area in
the parameter RAM of the serial channels. If an SDMA bus error occurs on a RISC-related
cycle, all CPM activity ceases and the entire communication processor module must be
reset in the CPM command register (CPCR).
EXTERNAL
RAM
1
INTERNAL U-BUS
SYSTEM
INTERFACE
UNIT
2
EXTERNAL
ROM
RISC
SDMA DUAL-PORT
MICROCONTROLLER
RAM
Figure 16-36. SDMA Data Paths
MOTOROLA MPC823e REFERENCE MANUAL 16-83