Return From An Interrupt Routine; Interrupt Hold Instructions - Oki ML63611 User Manual

ML63611 User's Manual
Chapter 4 Interrupt (INT)

4.3.2 Return from an Interrupt Routine

Return from a watchdog timer interrupt routine is performed with an "RTNMI" instruction.
Return from all other interrupt routines is performed with an "RTI" instruction.
Execution of "RTI" and "RTNMI" instructions both require 1 machine cycle.
When returning from an interrupt routine, the CPU performs the following processes.
(1) The call stack pointer (SP) is decremented by 1. (SP←SP–1)
(2) MIE is set to "1" (when an "RTNMI" instruction is used, MIE is restored to its state prior to the interrupt).
(3) 1 is added to the call stack contents and that value is loaded into the program counter (PC)
!
Note:
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While the MIE flag is "0" (interrupt disabled state), if a watchdog timer interrupt is processed and an "RTI"
instruction is executed, the MIE flag will be set to "1" and interrupts enabled.
•
Use "RTNMI" instructions to return from watchdog timer interrupts only. Use "RTI" instructions for normal
interrupts.

4.3.3 Interrupt Hold Instructions

Interrupt requests are not received after execution of interrupt hold instruction. They are received after execution
of an instruction other than interrupt hold instructions.
The interrupt hold instructions follow.
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ROM table reference instructions
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Stack operation instructions
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Jump instructions
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Conditional branch instructions
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Call/return instructions
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"EI" (set MIE flag) instructions, "DI" (clear MIE flag) instructions and "MSA cadr15" (start melody output)
instructions within control instructions
!
Note:
If interrupt hold instructions are to be used consecutively, consider that a generated interrupt will be put on hold for a
considerable amount of time before the interrupt routine begins.
OPTION A (C): 1.5 V (3.0 V), Without regulator
circuit for LCD bias
4 – 12
OPTION B (D): 1.5 V (3.0 V), With regulator
circuit for LCD bias