Development Support
Monitor ROM (MON)
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.
SENT TO
MONITOR
READ
READ
ADDR. HIGH ADDR. HIGH ADDR. LOW ADDR. LOW
DATA
ECHO
RESULT
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.
MISSING STOP BIT
2--STOP-BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
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
MC68HC908MR32 • MC68HC908MR16 — Rev. 6.0
MOTOROLA
Data Sheet
283
Development Support
FREESCALE [ Freescale ]
