UPD17P136ACT datasheet(79/292 Pages) NEC

79 / 292 page

CHAPTER 7 SYSTEM REGISTER (SYSREG)

7.7.2 Functions of the Program Status Word

The flags of the program status word are used for setting conditions for arithmetic operations and data transfer

instructions and for reflecting the status of operation results. Figure 7-18 shows an outline of the functions of the

program status word.

Figure 7-18. Outline of Functions of the Program Status Word

b3 b2 b1 b0

PSW

RPL

7FH

7EH

Address

Symbol

Bit

Flag

Used to specify that index modification be performed on the data

memory address used when a data memory manipulation instruction

is executed.

0: Index modification disabled.

1: Index modification enabled.

Flag

Function

IXE

CMP

BCD

Set when the result of an arithmetic operation is 0.

0: Indicates that the result of the arithmetic operation is a value other

than 0.

1: Indicates that the result of the arithmetic operation is 0.

Set when there is a carry in the result of an addition operation or

a borrow in the result of a subtraction operation.

0: Indicates there was no carry or borrow.

1: Indicates there was a carry or borrow.

Used to specify that the result of an arithmetic operation not be

stored in data memory or the general register but just be reflected

in the CY and Z flags.

0: Results of arithmetic operations are stored.

1: Results of arithmetic operations are not stored.

Used to specify how arithmetic operations are performed.

0: Arithmetic operations are performed in 4-bit binary.

1: Arithmetic operations are performed in BCD.

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