MB91233L Datasheet, PDF (22/66 Pages) Fujitsu Component Limited. – 32-bit Microcontroller

MB91230 Series
Notes on the PS register
As the PS register is processed by some instructions in advance, exception handling below may cause the
interrupt handling routine to break when the debugger is used or the display contents of flags in the PS register
to be updated.
As the microcontroller is designed to carry out reprocessing correctly upon returning from such an EIT event, it
performs operations before and after the EIT as specified in either case.
• The following operations may be performed when the instruction immediately followed by a DIVOU/DIVOS
instruction is (a) acceptance of a user interrupt, (b) single-stepped, or (c) breaks in response to a data event
or emulator menu :
1) The D0 and D1 flags are updated in advance.
2) An EIT handling routine (user interrupt or emulator) is executed.
3) Upon returning from the EIT, the DIVOU/DIVOS instruction is executed, and the D0 and D1 flags are updated
to the same values as in 1).
• The following operations are performed when the ORCCR/STILM/MOVRi and PS instructions are executed
to allow the interrupt.
1) The PS register is updated in advance.
2) An EIT handling routine (user interrupt) is executed.
3) Upon returning from the EIT, the above instructions are executed, and the PS register is updated to the
same value as in 1).
Watchdog Timer
The watchdog timer built in this model monitors a program that it defers a reset within a certain period of time.
The watchdog timer resets the CPU if the program runs out of controls, preventing the reset defer function from
being executed. Once the function of the watchdog timer is enabled, therefore, the watchdog timer keeps on
operating programs until it resets the CPU.
As an exception, the watchdog timer defers a reset automatically under the condition in which the CPU stops
program execution.
For those conditions to which this exception applies, see the function description of watchdog timer.
Step execution of RETI instruction
If an interrupt occurs frequently during step execution, the corresponding interrupt handling routine is executed
repeatedly after step execution. This will prevent the main routine and low-interrupt-level programs from being
executed.
Do not execute step of RETI instruction for escape.
Disable the corresponding interrupt and execute debugger when the corresponding interrupt routine no longer
needs debugging.
Operand Break
Do not apply a data event break to access to the area containing the address of a system stack pointer.
22