PIC16C923-04I/CL Microchip Technology, PIC16C923-04I/CL Datasheet - Page 23

• Manufacturer Part Number: PIC16C923-04I/CL
• Description: 8-Bit CMOS Microcontroller with LCD Driver
• Manufacturer: Microchip Technology

4.2.2.1
The STATUS register, shown in Figure 4-3, contains the
arithmetic status of the ALU, the RESET status and the
bank select bits for data memory.
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).
FIGURE 4-3: STATUS REGISTER (ADDRESS 03h, 83h, 103h, 183h)
1997 Microchip Technology Inc.
bit7
bit 7:
bit 6-5: RP1:RP0: Register Bank Select bits (used for direct addressing)
bit 4:
bit 3:
bit 2:
bit 1:
bit 0:
R/W-0
IRP
STATUS REGISTER
IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h - 1FFh)
0 = Bank 0, 1 (00h - FFh)
11 = Bank 3 (180h - 1FFh)
10 = Bank 2 (100h - 17Fh)
01 = Bank 1 (80h - FFh)
00 = 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) (for borrow the polarity is reversed)
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: 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.
R/W-0
RP1
R/W-0
RP0
R-1
TO
R-1
PD
R/W-x
Z
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.”
Note 1: The C and DC bits operate as a borrow
R/W-x
DC
and digit borrow bit, respectively, in sub-
traction. See the SUBLW and SUBWF
instructions for examples.
R/W-x
C
bit0
R = Readable bit
W = Writable bit
U = Unimplemented bit,
- n = Value at POR reset
PIC16C9XX
read as ‘0’
DS30444E - page 23