PIC16LC505-20I/P データシートの表示（PDF） - Microchip Technology

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PIC16LC505-20I/P

14-Pin, 8-Bit CMOS Microcontroller

Microchip Technology 

PIC16C505

4.3 STATUS Register

This register contains the arithmetic status of the ALU,

the RESET status and the page preselect bit.

The STATUS register can be the destination for any

instruction, as with any other register. If the STATUS

register is the destination for an instruction that affects

the Z, DC or C bits, then the write to these three bits is

disabled. These bits are set or cleared according to

the device logic. Furthermore, the TO and PD bits are

not writable. Therefore, the result of an instruction with

the STATUS register as destination may be different

than intended.

For example, CLRF STATUS will clear the upper three

bits and set the Z bit. This leaves the STATUS register

as 000u u1uu (where u = unchanged).

It is recommended, therefore, that only BCF, BSF and

MOVWF instructions be used to alter the STATUS

register, because these instructions do not affect the

Z, DC or C bits from the STATUS register. For other

instructions, which do affect STATUS bits, see

Instruction Set Summary.

REGISTER 4-1: STATUS REGISTER (ADDRESS:03h)

R/W-0 R/W-0 R/W-0

R-1

R-1

R/W-x

RBWUF —

PA0

TO

PD

Z

bit7

6

5

4

3

2

bit 7:

RBWUF: I/O reset bit

1 = Reset due to wake-up from SLEEP on pin change

0 = After power up or other reset

R/W-x

DC

1

R/W-x

C

bit0

R = Readable bit

W = Writable bit

U = Unimplemented bit,

read as ‘0’

- n = Value at POR reset

bit 6: Unimplemented

bit 5:

PA0: Program page preselect bits

1 = Page 1 (200h - 3FFh)

0 = Page 0 (000h - 1FFh)

Each page is 512 bytes.

Using the PA0 bit as a general purpose read/write bit in devices which do not use it for program

page preselect is not recommended, since this may affect upward compatibility with future products.

bit 4:

TO: Time-out bit

1 = After power-up, CLRWDT instruction, or SLEEP instruction

0 = A WDT time-out occurred

bit 3:

PD: Power-down bit

1 = After power-up or by the CLRWDT instruction

0 = By execution of the SLEEP instruction

bit 2:

Z: Zero bit

1 = The result of an arithmetic or logic operation is zero

0 = The result of an arithmetic or logic operation is not zero

bit 1:

DC: Digit carry/borrow bit (for ADDWF and SUBWF instructions)

ADDWF

1 = A carry from the 4th low order bit of the result occurred

0 = A carry from the 4th low order bit of the result did not occur

SUBWF

1 = A borrow from the 4th low order bit of the result did not occur

0 = A borrow from the 4th low order bit of the result occurred

bit 0:

C: Carry/borrow bit (for ADDWF, SUBWF and RRF, RLF instructions)

ADDWF

SUBWF

1 = A carry occurred

1 = A borrow did not occur

0 = A carry did not occur

0 = A borrow occurred

RRF or RLF

Load bit with LSB or MSB, respectively

DS40192C-page 14

© 1999 Microchip Technology Inc.

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