SN8P2318 Series
C-type LCD, RFC 8-Bit Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 35
Version 1.5
2.4.3 STACK OPERATION EXAMPLE
The two kinds of Stack-Save operations refer to the stack pointer (STKP) and write the content of program counter (PC)
to the stack buffer are CALL instruction and interrupt service. Under each condition, the STKP decreases and points to
the next available stack location. The stack buffer stores the program counter about the op-code address. The
Stack-Save operation is as the following table.
Stack Level
STKP Register
Stack Buffer
Description
STKPB2
STKPB1
STKPB0
High Byte
Low Byte
0
1
1
1
Free
Free
-
1
1
1
0
STK0H
STK0L
-
2
1
0
1
STK1H
STK1L
-
3
1
0
0
STK2H
STK2L
-
4
0
1
1
STK3H
STK3L
-
5
0
1
0
STK4H
STK4L
-
6
0
0
1
STK5H
STK5L
-
7
0
0
0
STK6H
STK6L
-
8
1
1
1
STK7H
STK7L
-
> 8
1
1
0
-
-
Stack Over, error
There are Stack-Restore operations correspond to each push operation to restore the program counter (PC). The RETI
instruction uses for interrupt service routine. The RET instruction is for CALL instruction. When a pop operation occurs,
the STKP is incremented and points to the next free stack location. The stack buffer restores the last program counter
(PC) to the program counter registers. The Stack-Restore operation is as the following table.
Stack Level
STKP Register
Stack Buffer
Description
STKPB2
STKPB1
STKPB0
High Byte
Low Byte
8
1
1
1
STK7H
STK7L
-
7
0
0
0
STK6H
STK6L
-
6
0
0
1
STK5H
STK5L
-
5
0
1
0
STK4H
STK4L
-
4
0
1
1
STK3H
STK3L
-
3
1
0
0
STK2H
STK2L
-
2
1
0
1
STK1H
STK1L
-
1
1
1
0
STK0H
STK0L
-
0
1
1
1
Free
Free
-