INSTRUCTION SET

S3C84E5/C84E9/P84E9

 

 

SUB — Subtract

SUBdst,src

Operation: dst dst – src

The source operand is subtracted from the destination operand and the result is stored in the destination. The contents of the source are unaffected. Subtraction is performed by adding the two's complement of the source operand to the destination operand.

Flags:

C: Set if a "borrow" occurred; cleared otherwise.

 

Z: Set if the result is "0"; cleared otherwise.

 

S: Set if the result is negative; cleared otherwise.

 

V: Set if arithmetic overflow occurred, that is, if the operands were of opposite signs and the

 

sign of the result is of the same as the sign of the source operand; cleared otherwise.

 

D: Always set to "1".

 

H: Cleared if there is a carry from the most significant bit of the low-order four bits of the

 

result; set otherwise indicating a “borrow”.

 

 

 

 

Format:

 

 

 

 

 

 

 

 

 

 

 

Bytes

Cycles

Opcode

Addr Mode

 

 

 

 

 

 

(Hex)

dst

src

 

 

 

 

 

 

 

 

 

 

opc

dst src

 

2

4

22

r

r

 

 

 

 

 

6

23

r

lr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

opc

src

dst

3

6

24

R

R

 

 

 

 

 

6

25

R

IR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

opc

dst

src

3

6

26

R

IM

 

 

 

 

 

 

 

 

 

Examples:

Given:

R1 = 12H, R2

= 03H, register 01H = 21H, register 02H = 03H, register 03H = 0AH:

 

SUB

R1,R2

R1

= 0FH, R2 = 03H

 

 

 

SUB

R1,@R2

R1

= 08H, R2 = 03H

 

 

 

SUB

01H,02H

Register 01H

=

1EH, register 02H

=

03H

 

SUB

01H,@02H

Register 01H

=

17H, register 02H

=

03H

 

SUB

01H,#90H

Register 01H

=

91H; C, S, and V

=

"1"

 

SUB

01H,#65H

Register 01H

=

0BCH; C and S =

"1", V = "0"

In the first example, if he working register R1 contains the value 12H and if the register R2 contains the value 03H, the statement "SUB R1,R2" subtracts the source value (03H) from the destination value (12H) and stores the result (0FH) in the destination register R1.

6-82

Page 209
Image 209
Samsung S3C84E5 user manual SUB Subtract