PIC16F630/676
2.2.2.1
STATUS Register
The STATUS register, shown in Register 2-1, contains:
• the arithmetic status of the ALU
• the RESET status
• the bank select bits for data memory (SRAM)
The STATUS register can be the destination for any
instruction, like 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.
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, see the “Instruction Set
Summary”.
Note 1:
Bits IRP and RP1 (STATUS<7:6>) are not
used by the PIC16F630/676 and should
be maintained as clear. Use of these bits
is not recommended, since this may affect
upward compatibility with future products.
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.
REGISTER 2-1:
STATUS — STATUS REGISTER (ADDRESS: 03h OR 83h)
Reserved Reserved
IRP
bit 7
RP1
R/W-0
RP0
R-1
TO
R-1
PD
R/W-x
Z
R/W-x
DC
R/W-x
C
bit 0
bit 7
bit 6
bit 5
IRP:
This bit is reserved and should be maintained as ‘0’
RP1:
This bit is reserved and should be maintained as ‘0’
RP0:
Register Bank Select bit (used for direct addressing)
1
= Bank 1 (80h - FFh)
0
= Bank 0 (00h - 7Fh)
TO:
Time-out bit
1
= After power-up,
CLRWDT
instruction, or
SLEEP
instruction
0
= A WDT time-out occurred
PD:
Power-down bit
1
= After power-up or by the
CLRWDT
instruction
0
= By execution of the
SLEEP
instruction
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,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
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.
bit 4
bit 3
bit 2
bit 1
bit 0
Legend:
R = Readable bit
- n = Value at POR
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared
x = Bit is unknown
©
2007 Microchip Technology Inc.
DS40039E-page 11
MICROCHIP [ MICROCHIP TECHNOLOGY ]
