PIC16F7X
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).
2.2.2.1
STATUS Register
The STATUS register contains the arithmetic status of
the ALU, the RESET status and the bank select bits for
data memory.
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."
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 1: 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.
REGISTER 2-1:
STATUS REGISTER (ADDRESS 03h, 83h, 103h, 183h)
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
bit 7
bit 0
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)
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, SUBWFinstructions)
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.
Legend:
R = Readable bit
- n = Value at POR reset
W = Writable bit
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared x = Bit is unknown
’1’ = Bit is set
2002 Microchip Technology Inc.
DS30325B-page 19
MICROCHIP [ MICROCHIP ]
