MC68HC908AZ60 Datasheet, PDF (174/480 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Monitor ROM (MON)
Echoing
As shown in Figure 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.
SENT TO
MONITOR
ECHO
READ
READ
ADDR. HIGH ADDR. HIGH ADDR. LOW ADDR. LOW
DATA
Figure 4. Read Transaction
RESULT
Break Signal
A start bit followed by nine low bits is a break signal. (See Figure 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.
MISSING STOP BIT
TWO-STOP-BIT DELAY BEFORE ZERO ECHO
01234567
01234567
Figure 5. Break Transaction
MC68HC908AZ60 — Rev 2.0
172
Monitor ROM (MON)
6-mon
MOTOROLA