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* This specification are subject to be changed without notice.

EM73C63

4-BIT MICRO-CONTROLLER FOR LCD PRODUCT

Preliminary

8.11.2000

ALU

The arithematic operation of 4 - bit data is performed in ALU unit . There are 2 flags that can be affected by

the result of ALU operation, ZF and SF . The operation of ALU is affected by CF only .

ALU STRUCTURE

ALU supported user arithematic operation functions, including Addition, Subtraction and Rotaion.

ALU FUNCTION

(1) Addition:

ALU supports addition function with instructions ADDAM, ADCAM, ADDM #k, ADD #k,y .... .

The addition operation affects CF and ZF. Under addition operation, if the result is "0", ZF will be "1",

otherwise, ZF will be "0", When the addition operation has a carry-out. CF will be "1", otherwise, CF will

be "0".

EXAMPLE:

Operation

Carry

Zero

3+4=7

0

0

7+F=6

1

0

0+0=0

0

1

8+8=0

1

1

(2) Subtraction:

ALU supports subtraction function with instructions SUBM #k, SUBA #k, SBCAM, DECM... . The

subtraction operation affects CF and ZF, Under subtraction operation, if the result is negative, CF will

be "0", and a borrow out, otherwise, if the result is positive, CF will be "1". For ZF, if the result of subtraction

operation is "0", the ZF is "1", likewise, ZF is "1".

EXAMPLE:

Operation

Carry

Zero

8-4=4

1

0

7-F= -8(1000)

0

0

9-9=0

1

1

ZF CF SF

ALU

DATA BUS