Datasheet

Monitor ROM (MON)
MC68HC908AP Family Data Sheet, Rev. 4
124 Freescale Semiconductor
The MCU executes the SWI and PSHH instructions when it enters monitor mode. The RUN command
tells the MCU to execute the PULH and RTI instructions. Before sending the RUN command, the host can
modify the stacked CPU registers to prepare to run the host program. The READSP command returns
the incremented stack pointer value, SP + 1. The high and low bytes of the program counter are at
addresses SP + 5 and SP + 6.
Table 8-8. READSP (Read Stack Pointer) Command
Description Reads stack pointer
Operand None
Data
Returned
Returns incremented stack pointer value (SP + 1) in
high-byte:low-byte order
Opcode $0C
Command Sequence
Table 8-9. RUN (Run User Program) Command
Description Executes PULH and RTI instructions
Operand None
Data
Returned
None
Opcode $28
Command Sequence
READSP
READSP
ECHO
FROM
HOST
SP
RETURN
SP
HIGH LOW
RUN
RUN
ECHO
FROM
HOST