SN8A1702AX datasheet(30/112 Pages) SONIX

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Preliminary

SN8P1702A/SN8P1703A

8-bit micro-controller build-in 12-bit ADC

SONiX TECHNOLOGY CO., LTD

Page 30

Revision 0.5

STACK REGISTERS

The stack pointer (STKP) is a 4-bit register to store the address used to access the stack buffer, 12-bits data memory

(STKnH and STKnL) set aside for temporary storage of stack addresses.

The two stack operations are writing to the top of the stack (Stack-Save) and reading (Stack-Restore) from the top of

stack. Stack-Save operation decrements the STKP and the Stack-Restore operation increments one time. That makes

the STKP always points to the top address of stack buffer and writes the last program counter value (PC) into the stack

buffer.

The program counter (PC) value is stored in the stack buffer before a CALL instruction executed or during interrupt

service routine. Stack operation is a LIFO type (Last in and first out). The stack pointer (STKP) and stack buffer

(STKnH and STKnL) are located in the system register area bank 0.

STKP (stack pointer) initial value = 0xxx 1111

0DFH

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

STKP

GIE

STKPB3

STKPB2

STKPB1

STKPB0

R/W

STKPBn: Stack pointer. (n = 0 ~ 3)

GIE: Global interrupt control bit. 0 = disable, 1 = enable. More detail information is in interrupt chapter.

Example: Stack pointer (STKP) reset routine.

MOV

A, #00001111B

B0MOV

STKP, A

STKn (stack buffer) initial value = xxxx xxxx xxxx xxxx, STKn = STKnH + STKnL (n = 7 ~ 0)

0F0H~0FFH

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

STKnH

SnPC9

SnPC8

R/W

0F0H~0FFH

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

STKnL

SnPC7

SnPC6

SnPC5

SnPC4

SnPC3

SnPC2

SnPC1

SnPC0

R/W

STKnH: Store PCH data as interrupt or call executing. The n expressed 0 ~7.

STKnL: Store PCL data as interrupt or call executing. The n expressed 0 ~7.

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