UPD17073 NEC, UPD17073 Datasheet - Page 37

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UPD17073

Manufacturer Part Number
UPD17073
Description
4-BIT SINGLE-CHIP MICROCONTROLLER WITH HARDWARE FOR DIGITAL TUNING SYSTEM
Manufacturer
NEC
Datasheet

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5.4.2 Functions of program status word
transfer operations, and indicates the results of the operations.
5.4.3 Notes on using program status word
of the arithmetic operation is stored in the program status word.
0000B is stored in PSW.
5.5 Notes on Using System Register
b
The program status word sets conditions, under which the ALU (Arithmetic Logic Unit) performs arithmetic or
Table 5-2 outlines the function of each flag of the program status word.
For details, refer to 7. ALU (Arithmetic Logic Unit) BLOCK.
When an arithmetic operation (addition or subtraction) instruction is executed to the program status word, the result
Even if an operation that generates a carry has been executed, for example, if the result of the operation is 0000B,
The data in the system register which are fixed to “0” are not influenced even when a write instruction is executed.
When these data are read, “0” is always read.
3
(RP)
b
RPL
2
b
1
b
B
C
D
word (PSWORD)
0
Program status
M
C
P
b
3
Table 5-2. Functional Outline of Each Flag of Program Status Word
C
Y
b
PSW
2
Z
b
1
b
0
0
Zero flag (Z)
Carry flag (CY)
Compare flag (CMP)
BCD flag (BCD)
Flag name
Indicates that the result of arithmetic operation is 0. Con-
dition under which this flag is set differs depending on
contents of compare flag.
Indicates occurrence of carry or borrow as a result of
executing addition or subtraction instruction.
Reset (0) when carry or borrow does not occur. Set (1) when
carry or borrow occurs. Also used as shift bit of "RORC r"
instruction.
Stores or does not store result of arithmetic operation in
data memory or general register.
Executes arithmetic operation in decimal.
0: Stores result
1: Does not store result
0: Executes binary operation
1: Executes decimal operation
Function
PD17072,17073
37

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