PIC16C5X
not writable. Therefore, the result of an instruction with
the STATUS register as destination may be different
than intended.
4.3
STATUS Register
This register contains the arithmetic status of the ALU,
the RESET status, and the page preselect bits for
program memories larger than 512 words.
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).
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
It is recommended, therefore, that only BCF, BSFand
MOVWFinstructions be used to alter the STATUS
register because these instructions do not affect the Z,
DC or C bits from the STATUS register. For other
instructions, which do affect STATUS bits, see
Section 8.0, Instruction Set Summary.
FIGURE 4-8: STATUS REGISTER (ADDRESS:03h)
R/W-0
PA2
R/W-0
PA1
R/W-0
PA0
R-1
TO
R-1
PD
R/W-x
Z
R/W-x
DC
R/W-x
C
R = Readable bit
W = Writable bit
- n = Value at POR reset
bit7
6
5
4
3
2
1
bit0
bit 7:
PA2: This bit unused at this time.
Use of the PA2 bit as a general purpose read/write bit is not recommended, since this may affect upward
compatibility with future products.
bit 6-5: PA1:PA0: Program page preselect bits (PIC16C56s/CR56s)(PIC16C57s/CR57s)(PIC16C58s/CR58s)
00 = Page 0 (000h - 1FFh) - PIC16C56s/CR56s, PIC16C57s/CR57s, PIC16C58s/CR58s
01 = Page 1 (200h - 3FFh) - PIC16C56s/CR56s, PIC16C57s/CR57s, PIC16C58s/CR58s
10 = Page 2 (400h - 5FFh) - PIC16C57s/CR57s, PIC16C58s/CR58s
11 = Page 3 (600h - 7FFh) - PIC16C57s/CR57s, PIC16C58s/CR58s
Each page is 512 words.
Using the PA1:PA0 bits as general purpose read/write bits in devices which do not use them for program
page preselect is not recommended since this may affect upward compatibility with future products.
bit 4:
bit 3:
bit 2:
bit 1:
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 (for ADDWFand SUBWFinstructions)
ADDWF
1 = A carry from the 4th low order bit of the result occurred
0 = A carry from the 4th low order bit of the result did not occur
SUBWF
1 = A borrow from the 4th low order bit of the result did not occur
0 = A borrow from the 4th low order bit of the result occurred
bit 0:
C: Carry/borrow bit (for ADDWF, SUBWFand RRF, RLFinstructions)
ADDWF
SUBWF
RRF or RLF
1 = A carry occurred
0 = A carry did not occur
1 = A borrow did not occur
0 = A borrow occurred
Load bit with LSb or MSb, respectively
DS30453B-page 20
Preliminary
1998 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
