Datasheet

Development Support
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
178 Freescale Semiconductor
16.3.1.10 Commands
The monitor ROM firmware uses these commands:
• READ, read memory
• WRITE, write memory
• IREAD, indexed read
• IWRITE, indexed write
• READSP, read stack pointer
• RUN, run user program
The monitor ROM firmware echoes each received byte back to the PTA0 pin for error checking. An 11-bit
delay at the end of each command allows the host to send a break character to cancel the command. A
delay of two bit times occurs before each echo and before READ, IREAD, or READSP data is returned.
The data returned by a read command appears after the echo of the last byte of the command.
NOTE
Wait one bit time after each echo before sending the next byte.
Figure 16-12. Read Transaction
Figure 16-13. Write Transaction
READREAD
ECHO
FROM
HOST
ADDRESS
HIGH
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
RETURN
13, 2114
4
Notes:
2 = Data return delay, 2 bit times
3 = Cancel command delay, 11 bit times
4 = Wait 1 bit time before sending next byte.
4 4
1 = Echo delay, 2 bit times
WRITE
WRITE
ECHO
FROM
HOST
ADDRESS
HIGH
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
DATA
Notes:
3 = Cancel command delay, 11 bit times
4 = Wait 1 bit time before sending next byte.
114114
4
43, 4
1 = Echo delay, 2 bit times