GMS81C50 Datasheet, PDF (25/99 Pages) Hynix Semiconductor – 8-BIT SINGLE CHIP MICROCONTROLLERS

GMS81C50 Series
used.
Stack Address ( 100_H ~ 1FF_H )
15
87
0
1
SP
Hardware fixed
HYUNDAI
Caution:
The Stack Pointer must be initialized by software be-
cause its value is undefined after RESET.
Example: To initialize the SP
LDX #0FFH
TXSP
; SP ← FF_H
At execution of
a CALL/TCALL/PCALL
At acceptance
of interrupt
At execution
of RET instruction
01FC
01FD
01FE
01FF
PCL
PCH
Push
down
01FC
01FD
01FE
01FF
PSW
PCL
PCH
Push
down
01FC
01FD
01FE PCL
Pop
01FF PCH
up
SP before
execution
SP after
execution
01FF
01FD
01FF
01FC
01FD
01FF
At execution
of PUSH instruction
PUSH A (X,Y,PSW)
01FC
01FD
01FE
01FF
A
Push
down
SP before
execution
SP after
execution
01FF
01FE
At execution
of POP instruction
POP A (X,Y,PSW)
01FC
01FD
01FE
01FF
A
Pop
up
01FE
01FF
Figure 8-3 Stack Operation
At execution
of RETI instruction
01FC
01FD PSW
01FE PCL
Pop
up
01FF PCH
01FC
01FF
0100H
Stack
depth
01FFH
Program Counter:
The Program Counter is a 16-bit wide which consists of
two 8-bit registers, PCH and PCL. This counter indicates
the address of the next instruction to be executed. In reset
state, the program counter has reset routine address
(PC_H:0FF_H, PC_L:0FE_H).
Program Status Word:
The Program Status Word (PSW) contains several bits that
reflect the current state of the CPU. The PSW is described
in Figure 8-4 . It contains the Negative flag, the Overflow
flag, the Break flag the Half Carry (for BCD operation),
the Interrupt enable flag, the Zero flag, and the Carry flag.
[Carry flag C]
This flag stores any carry or borrow from the ALU of CPU
after an arithmetic operation and is also changed by the
Shift Instruction or Rotate Instruction.
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