UPD17P136ACT datasheet(81/292 Pages) NEC

tên linh kiện	UPD17P136ACT

Giải thích chi tiết về linh kiện	4-BIT SINGLE-CHIP MICROCONTROLLER

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CHAPTER 7 SYSTEM REGISTER (SYSREG)

7.7.6 Binary-Coded Decimal Flag (BCD)

The BCD flag is used for BCD operations.

When the BCD flag is set (BCD = 1), all arithmetic operations will be performed in BCD. When the BCD flag is

reset (BCD = 0), arithmetic operations are performed in 4-bit binary.

The BCD flag does not affect logical operations, bit judgement, comparison judgement or rotations.

7.7.7 Notes Concerning Use of Arithmetic Operations

When performing arithmetic operations (addition and subtraction) on the program status word (PSWORD), the

following point should be kept in mind.

When an arithmetic operation is performed on the program status word, the result is stored in the program status

word.

Below is an example.

Example

MOV

PSW, #0001B

ADD

PSW, #1111B

When the above instructions are executed, a carry is generated which should cause bit 2 (CY flag) of

PSW to be set. However, the result of the operation (0000B) is stored in PSW, meaning that CY does

not get set.

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