RFPIC12C509AG Datasheet, PDF (20/104 Pages) Microchip Technology – 18/20-Pin 8-Bit CMOS Microcontroller with UHF ASK/FSK Transmitter

rfPIC12C509AG/509AF
4.3 STATUS Register
This register contains the arithmetic status of the ALU,
the RESET status, and the page preselect bit for pro-
gram memories larger than 512 words.
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.
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 and
MOVWF instructions be used to alter the STATUS regis-
ter because these instructions do not affect the Z, DC
or C bits from the STATUS register. For other instruc-
tions, which do affect STATUS bits, see Instruction Set
Summary.
figure 4-3:
STATUS REGISTER (ADDRESS:03h)
R/W-0 R/W-0 R/W-0
R-1
R-1
R/W-x
GPWUF —
PA0
TO
PD
Z
bit7
6
5
4
3
2
bit 7:
GPWUF: GPIO Reset bit
1 = Reset due to wake-up from SLEEP on pin change
0 = After power-up or other RESET
R/W-x
DC
1
R/W-x
C
bit0
R = Readable bit
W = Writable bit
- n = Value at POR Reset
bit 6: Unimplemented
bit 5:
PA0: Program page preselect bits
1 = Page 1 (200h - 3FFh)
0 = Page 0 (000h - 1FFh
Each page is 512 bytes.
Using the PA0 bit as a general purpose read/write bit in devices which do not use it for program
page preselect is not recommended since this may affect upward compatibility with future products.
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 (for ADDWF and SUBWF instructions)
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, SUBWF and RRF, RLF instructions)
ADDWF
SUBWF
1 = A carry occurred
1 = A borrow did not occur
0 = A carry did not occur
0 = A borrow occurred
RRF or RLF
Load bit with LSB or MSB, respectively
DS70031A-page 18
Preliminary
© 2001 Microchip Technology Inc.