PIC16C71X
4.2.2.1
STATUS REGISTER
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 the Z, C or DC bits from the STATUS register. For
other instructions, not affecting any status bits, see the
"Instruction Set Summary."
Applicable Devices 710 71 711 715
The STATUS register, shown in Figure 4-7, contains
the arithmetic status of the ALU, the RESET status and
the bank select bits for data memory.
Note 1: For those devices that do not use bits IRP
and RP1 (STATUS<7:6>), maintain these
bits clear to ensure upward compatibility
with future products.
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.
Note 2: The C and DC bits operate as a borrow
and digit borrow bit, respectively, in sub-
traction. See the SUBLW and SUBWF
instructions for examples.
For example, CLRF STATUSwill clear the upper-three
bits and set the Z bit. This leaves the STATUS register
as 000u u1uu(where u= unchanged).
FIGURE 4-7: STATUS REGISTER (ADDRESS 03h, 83h)
R/W-0
IRP
R/W-0
RP1
R/W-0
RP0
R-1
TO
R-1
PD
R/W-x
Z
R/W-x
DC
R/W-x
C
R = Readable bit
W = Writable bit
bit7
bit0
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
bit 7:
IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h - 1FFh)
0 = Bank 0, 1 (00h - FFh)
bit 6-5: RP1:RP0: Register Bank Select bits (used for direct addressing)
11= Bank 3 (180h - 1FFh)
10= Bank 2 (100h - 17Fh)
01= Bank 1 (80h - FFh)
00= Bank 0 (00h - 7Fh)
Each bank is 128 bytes
bit 4:
bit 3:
bit 2:
bit 1:
bit 0:
TO: Time-out bit
1 = After power-up, CLRWDTinstruction, or SLEEPinstruction
0 = A WDT time-out occurred
PD: Power-down bit
1 = After power-up or by the CLRWDTinstruction
0 = By execution of the SLEEPinstruction
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
DC: Digit carry/borrow bit (ADDWF, ADDLW,SUBLW,SUBWFinstructions)(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
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.
1997 Microchip Technology Inc.
DS30272A-page 17
MICROCHIP [ MICROCHIP ]
