41594B datasheet(18/372 Pages) MICROCHIP

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PIC12LF1840T48A

DS41594B-page 18

Preliminary

 2011-2012 Microchip Technology Inc.

3.2.1.1

STATUS Register

The STATUS register, shown in Register 3-1, contains:

• the arithmetic status of the ALU

• the Reset status

The STATUS register can be the destination for any

instruction, like 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).

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

SWAPF and MOVWF instructions are used to alter the

STATUS register, because these instructions do not

affect any Status bits. For other instructions not

affecting any Status bits (Refer to Section 30.0

“Instruction Set Summary”).

Note 1: The C and DC bits operate as Borrow

and Digit Borrow out bits, respectively, in

subtraction.

STATUS: STATUS REGISTER

U-0

R-1/q

R/W-0/u

—

ZDC(1)

C(1)

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

u = Bit is unchanged

x = Bit is unknown

-n/n = Value at POR and BOR/Value at all other Resets

‘1’ = Bit is set

‘0’ = Bit is cleared

q = Value depends on condition

bit 7-5

Unimplemented: Read as ‘0’

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/Digit Borrow bit(1)

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

0 = No carry-out from the 4th low-order bit of the result

bit 0

C: Carry/Borrow bit(1)

1 = A carry-out from the Most Significant bit of the result occurred

0 = No carry-out from the Most Significant bit of the result occurred

Note 1:

For Borrow, the polarity is reversed. A subtraction is executed by adding the two’s complement of the

second operand.

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