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EM73P982H

4-BIT MICROCONTROLLER

ELAN Microelectronics 

EM73P982

4-BIT MICROCONTROLLER

(2) Subtraction:

For instruction SUBM #k, SUBA #k, SBCAM, DECM... ALU supports user subtraction function. The

subtraction operation can affect CF and ZF, For subtraction operation, if the result is negative, CF will

be "0", it means 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 will be "1", otherwise, ZF will be "1".

EXAMPLE:

Operation

8-4=4

7-F= -8(1000)

9-9=0

Carry Zero

1

0

0

0

1

1

(3) Rotation:

There are two kinds of rotation operation, one is rotation left, the other is rotation right.

RLCA instruction rotates Acc value to left, shift the CF value into the LSB bit of Acc and the shift out data

will be hold in CF.

MSB LSB

ACC

CF

RRCA instruction operation rotates Acc value to right, shift the CF value into the MSB bit of Acc and the

shift out data will be hold in CF.

MSB LSB

ACC

CF

PROGRAM EXAMPLE: To rotate Acc right and shift a "1" into the MSB bit of Acc.

TTCFS; CF ← 1

RRCA; rotate Acc right and shift CF=1 into MSB.

HL REGISTER

HL register are two 4-bit registers, they are used as a pair of pointer for the address of RAM memory and also

2 independent temporary 4-bit data registers. For some instruction, L register can be a pointer to indicate the

pin number (Port4).

HL REGISTER STRUCTURE

3210 3210

H REGISTER L REGISTER

* This specification are subject to be changed without notice.

12.25.2001 6

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