PIC12F508_09 datasheet(22/110 Pages) MICROCHIP

22 / 110 page

PIC12F508/509/16F505

DS41236E-page 22

4.4

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

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).

Therefore, it is recommended that only BCF, BSF and

MOVWF

instructions be used to alter the STATUS regis-

ter. These instructions do not affect the Z, DC or C bits

from the STATUS register. For other instructions which

do affect Status bits, see Section 8.0 “Instruction Set

Summary”.

STATUS REGISTER (ADDRESS: 03h) (PIC12F508/509)

R/W-0

R-1

R/W-x

GPWUF

—PA0

ZDC

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7

GPWUF: GPIO Reset bit

= Reset due to wake-up from Sleep on pin change

= After power-up or other Reset

bit 6

Reserved: Do not use

bit 5

PA0: Program Page Preselect bits(1)

= Page 1 (200h-3FFh)

= 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

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

= A WDT time-out occurred

bit 3

PD: Power-Down bit

= After power-up or by the CLRWDT instruction

= By execution of the SLEEP instruction

bit 2

Z: Zero bit

= The result of an arithmetic or logic operation is zero

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

bit 1

DC: Digit Carry/Borrow bit (for ADDWF and SUBWF instructions)

ADDWF:

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

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

SUBWF:

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

= 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:

RRF

or RLF:

= A carry occurred

= A borrow did not occur

Load bit with LSb or MSb, respectively

= A carry did not occur

= A borrow occurred

Note

This bit is used on the PIC12F509. For code compatibility do not use this bit on the PIC12F508.

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