upd17225 Renesas Electronics Corporation., upd17225 Datasheet - Page 14

• Manufacturer Part Number: upd17225
• Description: 4-bit Single-chip Microcontroller For Small General-purpose Infrared Remote Control Transmitter
• Manufacturer: Renesas Electronics Corporation.

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2.3.2
(first instruction cycle) is executed or when an interrupt is accepted. It also stores the contents of the address registers
(ARs) when a stack manipulation instruction (PUSH AR) is executed.
(PSWORD) when an interrupt is accepted. The saved contents are restored when an interrupt return (RETI) instruction
is executed.
interrupts occur.
2.3.3
WDOUT pin goes low if the value of SP is 6 or greater.
CALL addr
CALL @AR
MOVT DBF, @AR
(1st Instruction Cycle)
PUSH AR
When Interrupt Is Accepted
RET
RETSK
MOVT DBF, @AR
(2nd Instruction Cycle)
POP AR
RETI
The address stack register stores a return address when the subroutine call instruction or table reference instruction
The WDOUT pin goes low if a subroutine call or interrupt exceeding 5 levels is executed.
The interrupt stack register (INTSK) saves the contents of the bank register (BANK) and program status word
INTSK saves data each time an interrupt is accepted, but the data stored first is lost if more than 3 levels of
Table 2-1 shows the operations of the stack pointer (SP).
The stack pointer can take eight values, 0H-07. Because there are only five stack registers available, however, the
Function of stack
Stack Pointer (SP) and Interrupt Stack Pointer
Instruction
Table 2-1. Operations of Stack Pointer
Data Sheet U12643EJ2V0DS00
Value of Stack Pointer (SP)
–1
–1
+1
+1
PD17225, 17226, 17227, 17228
Counter of Interrupt Stack Register
–1
+1
0
0