mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 124

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Monitor Mode (MON)
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.
8.4 Security
A security feature discourages unauthorized reading of FLASH locations while in monitor mode. The host
can bypass the security feature at monitor mode entry by sending eight security bytes that match the
bytes at locations $FFF6–$FFFD. Locations $FFF6–$FFFD contain user-defined data.
124
Do not leave locations $FFF6–$FFFD blank. For security reasons, program
locations $FFF6–$FFFD even if they are not used for vectors.
Description
Returned
Operand
Opcode
Data
Figure 8-7. Stack Pointer at Monitor Mode Entry
Table 8-9. RUN (Run User Program) Command
Executes PULH and RTI instructions
None
None
$28
MC68HC908AP A-Family Data Sheet, Rev. 3
HIGH BYTE OF PROGRAM COUNTER
LOW BYTE OF PROGRAM COUNTER
HIGH BYTE OF INDEX REGISTER
LOW BYTE OF INDEX REGISTER
CONDITION CODE REGISTER
ECHO
FROM
HOST
RUN
ACCUMULATOR
Command Sequence
NOTE
RUN
SP
SP + 1
SP + 2
SP + 3
SP + 4
SP + 5
SP + 6
SP + 7
Freescale Semiconductor