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MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
260 Freescale Semiconductor
18.3.1.5 Echoing
As shown in Figure 18-11, the monitor ROM immediately echoes each received byte back to the PTA0
pin for error checking.
Figure 18-11. Read Transaction
Any result of a command appears after the echo of the last byte of the command.
18.3.1.6 Break Signal
A start bit followed by nine low bits is a break signal. See Figure 18-12. 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 18-12. Break Transaction
18.3.1.7 Commands
The monitor ROM uses these commands (see Table 18-3Table 18-8):
READ, read memory
WRITE, write memory
IREAD, indexed read
IWRITE, indexed write
READSP, read stack pointer
RUN, run user program
ADDR. HIGHREADREAD ADDR. HIGH ADDR. LOW ADDR. LOW DATA
ECHO
SENT TO
MONITOR
RESULT
01234567 01234567
MISSING STOP BIT
2--STOP-BIT DELAY BEFORE ZERO ECHO