MPC823 datasheet(40/74 Pages) MOTOROLA

40 / 74 page

Communication Processor Module

16-418

MPC823 REFERENCE MANUAL

MOTOROLA

L— Last in Message

0 = The last byte in the buffer is not the last byte in the transmitted transparent frame.

Data from the next transmit buffer (if ready) is transmitted immediately following the

last byte of this buffer.

1 = The last byte in this buffer is the last byte in the transmitted transparent frame. After

this buffer is transmitted, the transmitter requires synchronization before the next

buffer is transmitted.

CM—Continuous Mode

0 = Normal operation.

1 = The communication processor module does not clear the R bit after this buffer

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

retransmitted next time the communication processor module accesses this buffer

descriptor. However, the R bit will be cleared if an error occurs during transmission,

regardless of how the CM bit is set.

UN—Underrun

This bit indicates that a serial management controller has encountered a transmitter

underrun condition while transmitting the associated data buffer.

DATA LENGTH

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

transmit from this data buffer and it is never modified by the communication processor

module. This field can be even or odd, but if the number of bits in the transparent character

is greater than 8, this field must be even. For example, to transmit three transparent 8-bit

characters, this field must be initialized to 3. However, to transmit three transparent 9-bit

characters, this field must be initialized to 6 since the three 9-bit characters occupy three

half-words in memory.

TX DATA BUFFER POINTER

This field always points to the first byte of the associated data buffer. They can be even or

odd, unless the character length is greater than 8 bits, in which case this field must be even.

For instance, the pointer to 8-bit transparent characters can be even or odd, but the pointer

to 9-bit transparent characters must be even. The buffer can reside in internal or external

memory.

MPC823 датащи(PDF) 40 Page - Motorola, Inc