Communications Processor (CP)
MOTOROLA
MC68302 USER’S MANUAL
4-111
T2,T1—Message Type
00 = Data message
01 = Control message
10 = Maintenance message
11 = Reserved
Bits 7–6—Reserved for future use.
CF—CRC Follow Error
The character following the CRC for this message was not one of SOH, ENQ, DLE, SYN,
or IDLE. The receiver then enters hunt mode.
FR—Framing Error
A character with a framing error was received. The associated character may be found at
the last location in this buffer. A framing error is detected by the UART controller when no
stop bit is detected in the receive data string.
NOTE
This error can occur only on asynchronous DDCMP links.
PR—Parity Error
A character with a parity error was received. The associated character may be found at
the last location in this buffer.
NOTE
This error can occur only on asynchronous DDCMP links.
CR—Rx CRC Error
A message with a CRC error was received in the header (CRC1) or data (CRC2) fields or
a control message (CRC3).
OV—Overrun
A receiver overrun occurred during message reception.
CD—Carrier Detect Lost
The CD signal was negated during message reception. This bit is valid only when working
in NMSI mode.
Data Length
The data length is the number of octets that the DDCMP controller has written to this BD's
data buffer. It is written by the CP once as the BD is closed.
NOTE
The actual buffer size should be greater than or equal to eight
(to ensure the header is received in one buffer).
