Monitor ROM (MON)
Table 8-8. READSP (Read Stack Pointer) Command
Description Reads stack pointer
Operand None
Data Returns incremented stack pointer value (SP + 1) in
Returned high-byte:low-byte order
Opcode $0C
Command Sequence
FROM
HOST
SP
HIGH
SP
LOW
READSP
READSP
ECHO
RETURN
Table 8-9. RUN (Run User Program) Command
Description Executes PULH and RTI instructions
Operand None
Data
None
Returned
Opcode $28
Command Sequence
FROM
HOST
RUN
RUN
ECHO
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.
MC68HC908AP Family Data Sheet, Rev. 4
124
Freescale Semiconductor
FREESCALE [ Freescale ]
