MPC823 datasheet(38/74 Pages) MOTOROLA

38 / 74 page

Communication Processor Module

16-416

MPC823 REFERENCE MANUAL

MOTOROLA

W—Wrap (Final Buffer Descriptor in Table)

0 = This is not the last buffer descriptor in the RX buffer descriptor table.

1 = This is the last buffer descriptor in the RX buffer descriptor table. After this buffer

is used, the communication processor module receives incoming data into the first

buffer descriptor that RBASE points to in the table. The number of RX buffer

descriptors in this table is programmable and determined only by the W bit and

overall space constraints of the dual-port RAM.

I—Interrupt

0 = No interrupt is generated after this buffer is filled.

1 = The RX bit in the SMCE–Transparent register is set when this buffer is completely

filled by the communication processor module, thus indicating that the core needs

to process the buffer. The RX bit can cause an interrupt if it is enabled.

CM—Continuous Mode

0 = Normal operation.

1 = The E bit is not cleared by the communication processor module after this buffer

descriptor is closed, thus allowing the associated data buffer to be automatically

overwritten next time the communication processor module accesses this buffer

descriptor. However, the E bit is cleared if an error occurs during reception,

regardless of how the CM bit is set.

OV—Overrun

This bit indicates that a receiver overrun has occurred during message reception. The

communication processor module writes this bit after the received data is placed into the

associated data buffer.

DATA LENGTH

This field represents the number of octets that the communication processor module writes

into this data buffer. It is only written once by the communication processor module as the

buffer is closed. The communication processor module writes this field after the received

data is placed into the associated data buffer.

RX DATA BUFFER POINTER

This field always points to the first location of the associated data buffer, must be even, and

can reside in internal or external memory. The communication processor module writes

these bits after the received data is placed into the associated data buffer.

Note: The actual amount of memory allocated for this buffer must be greater than or

equal to the MRBLR entry.

MPC823 Datasheet(PDF) 38 Page - Motorola, Inc