Freescale Semiconductor MC68HC908MR32 - Manual (Page 260)

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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 18-3 – Table 18-8 ):
• READ, read memory
• WRITE, write memory
• IREAD, indexed read
• IWRITE, indexed write
• READSP, read stack pointer
• RUN, run user program
ADDR. HIGH READ READ 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
2--STOP-BIT DELAY BEFORE ZERO ECHO