upd17240 Renesas Electronics Corporation., upd17240 Datasheet - Page 21

• Manufacturer Part Number: upd17240
• Description: 4-bit Single-chip Microcontrollers For Small General-purpose Infrared Remote Control Transmitters
• Manufacturer: Renesas Electronics Corporation.

2.3.2
instruction (first instruction cycle) is executed or when an interrupt is acknowledged. It also stores the contents of
the address registers (ARs) when a stack manipulation instruction (PUSH AR) is executed.
a reset is effected.
(PSWORD) when an interrupt is acknowledged. The saved contents are restored when an interrupt return (RETI)
instruction is executed.
of interrupts occur.
2.3.3
the RESET pin is internally pulled down and reset is effected if the value of SP is 6 or greater.
CALL addr
CALL @AR
MOVT DBF, @AR
(1st instruction cycle)
PUSH AR
SYSCAL entry
When interrupt is acknowledged
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
If subroutines or interrupts are nested to more than 5 levels, the RESET pin is internally pulled down and
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 acknowledged, but the data stored first is lost if more than 3 levels
Table 2-3 shows the operations of the stack pointer (SP).
The stack pointer can take eight values, 0H to 7H. Because there are only five stack registers available, however,
Function of stack
Stack pointer (SP) and interrupt stack pointer
Instruction
µ PD17240, 17241, 17242, 17243, 17244, 17245, 17246
Table 2-3. Operations of Stack Pointer
Value of Stack Pointer (SP)
Data Sheet U15002EJ1V1DS
−1
–1
+1
+1
Counter of Interrupt Stack Register
–1
+1
0
0
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