EM73PA88A
4-BIT MICRO-CONTROLLER FOR LCD PRODUCT
PROGRAM EXAMPLE:
Check following arithematic operation for CF, ZF, SF
CF
ZF
1
SF
1
LDIA #00h;
LDIA #03h;
ADDA #05h;
ADDA #0Dh;
ADDA #0Eh;
-
-
-
-
-
0
1
0
1
0
0
0
0
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.
DATA BUS
ALU
ZF CF SF
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
3+4=7
7+F=6
0+0=0
Carry Zero
0
1
0
1
0
0
1
1
8+8=0
(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".
* This specification are subject to be changed without notice.
10.8.2001
14
ELAN [ ELAN MICROELECTRONICS CORP ]
