CHAPTER 4: INSTRUCTION SET

DEC %sp

Decrement stack pointer

1 cycle

Function: sp ←

sp - 1

 

Decrements (-1) the content of the stack pointer sp (SP1 or SP2). This instruction does not change the C flag regardless of the operation result.

Code:

Mnemonic

 

 

MSB

 

 

 

 

 

 

 

 

 

 

LSB

 

 

DEC %SP1

 

1

 

1

1

1

1

1

1

1

0

0

0

0

 

0

1FE0H

 

DEC %SP2

 

1

 

1

1

1

1

1

1

1

0

0

1

0

 

0

1FE4H

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flags:

E

 

I

 

C

 

Z

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode:

Register direct

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Extended addressing: Invalid

 

 

 

 

 

 

 

 

 

 

 

 

EX %A,%B

Exchange A reg. and B reg.

1 cycle

Function: A ↔ B

 

 

Exchanges the contents of the A register and B register.

Code:

Mnemonic

 

 

MSB

 

 

 

 

 

 

 

LSB

 

EX %A,%B

 

 

1

1

1

1

1

1

1

1

1

0

1

1

1

1FF7H

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flags:

E

 

I

C

 

Z

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mode:

Src: Register direct

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dst: Register direct

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Extended addressing: Invalid

 

 

 

 

 

 

 

 

 

 

90

EPSON

S1C63000 CORE CPU MANUAL