
MOTOROLA
CONTROL AND STATUS CODES
MC68HC58
5-12
TECHNICAL DATA
5.4.1 ERRF — Error Bit
This bit indicates whether the receiver detected an error during the frame. When ERRF
is set, the ERRC field indicates which error occurred.
0 = No error occurred
1 = Error occurred
5.4.2 RFO — Receive FIFO Overrun Bit
When the RFO bit is set, a RxFIFO buffer overrun has occurred. This means that the
host MCU has not read the RxFIFO buffer regularly enough to prevent incoming frame
bytes from being lost. RFO is set when the first bit of the 21st data byte is received.
Previously received data bytes remain in the buffer. When RFO is set, no other com-
pletion code bits can be considered valid. There is no way to detect BREAK when the
buffer has overflowed.
0 = No receiver buffer overrun occurred
1 = Receiver buffer overrun occurred
5.4.3 TMS[5:4] — Transmitter Status Field
This bit field shows transmitter status during the frame just received. Table 5-7 shows
transmitter status field encoding.
5.4.3.1 Transmitter Not Involved
This value indicates that the transmitter did not perform J1850 bus contention for this
frame. Frame did not originate from this node.
5.4.3.2 Transmitter Underrun
This value indicates that a frame was transmitted but was not completed. This is not
an indication that the transmission lost J1850 bus contention.
CCBR — Completion Code Byte Register
7
6
5
4
3
2
1
0
ERRF
RFO
TMS
IFR
IFRC
ERRC
RESET
0
Table 5-7 TMS Field Encoding
Value
Description
00
Transmitter not involved
01
Transmitter underrun
10
Transmitter lost arbitration
11
Transmitter successful