Development Support
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
