Monitor ROM (MON)
Technical Data MC68HC908AB32 — Rev. 1.0
162 Monitor ROM (MON) MOTOROLA
10.4.3 Echoing
As shown in Figure 10-4, the monitor ROM immediately echoes each
received byte back to the PTA0 pin for error checking.
Any result of a command appears after the echo of the last byte of the
command.
Figure 10-4. Read Transaction
10.4.4 Break Signal
A start bit followed by nine low bits is a break signal. (See Figure 10-5.)
When the monitor receives a break signal, it drives the PTA0 pin high for
the duration of two bits before echoing the break signal.
Figure 10-5. Break Transaction
ADDR. HIGHREADREAD ADDR. HIGH ADDR. LOW ADDR. LOW DATA
ECHO
SENT TO
MONITOR
RESULT
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
MISSING STOP BIT
TWO-STOP-BIT DELAY BEFORE ZERO ECHO
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