PIC16LC554 datasheet(17/96 Pages) MICROCHIP

17 / 96 page

Preliminary

DS40143B-page 17

PIC16C55X(A)

4.2.2.1

STATUS REGISTER

The STATUS register, shown in Figure 4-6, contains

the arithmetic status of the ALU, the RESET status and

the bank select bits for data memory.

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 the 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

000uu1uu

(where u = unchanged).

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

SWAPF

and MOVWF instructions be used to alter the STA-

TUS register because these instructions do not affect

any status bits. For other instructions, not affecting any

status bits, see the “Instruction Set Summary”.

Note 1:

The IRP and RP1 bits (STATUS<7:6>)

are not used by the PIC16C55X(A) and

should be programmed as ’0'. Use of

these bits as general purpose R/W bits is

NOT recommended, since this may

affect upward compatibility with future

products.

Note 2:

The C and DC bits operate as a Borrow

and Digit Borrow out bit, respectively, in

subtraction. See the SUBLW and SUBWF

instructions for examples.

FIGURE 4-6:

STATUS REGISTER (ADDRESS 03H OR 83H)

Reserved Reserved

R/W-0

R-1

R/W-x

IRP

RP1

RP0

= Readable bit

W = Writable bit

- n = Value at POR reset

- x = Unknown at POR reset

bit7

bit0

bit 7:

IRP: Register Bank Select bit (used for indirect addressing)

1 = Bank 2, 3 (100h - 1FFh)

0 = Bank 0, 1 (00h - FFh)

The IRP bit is reserved on the PIC16C55X(A), always maintain this bit clear.

bit 6-5: RP1:RP0: Register Bank Select bits (used for direct addressing)

= Bank 3 (180h - 1FFh)

= Bank 2 (100h - 17Fh)

= Bank 1 (80h - FFh)

= Bank 0 (00h - 7Fh)

Each bank is 128 bytes. The RP1 bit is reserved on the PIC16C55X(A), always maintain this bit clear.

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 (ADDWF, ADDLW,SUBLW,SUBWF instructions)(for borrow the polarity is reversed)

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 (ADDWF, ADDLW,SUBLW,SUBWF instructions)

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

second operand. For rotate (RRF, RLF) instructions, this bit is loaded with either the high or low order bit of

the source register.

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