PIC24FV16KM204 FAMILY
DS33030A-page 38
Advance Information
2013 Microchip Technology Inc.
3.2
CPU Control Registers
REGISTER 3-1:
SR: ALU STATUS REGISTER
U-0
U-0
U-0
U-0
U-0
U-0
U-0
R/W-0, HSC
—
—
—
—
—
—
—
DC
bit 15
bit 8
R/W-0, HSC
R/W-0, HSC
)
R/W-0, HSC
(
)
R-0, HSC R/W-0, HSC R/W-0, HSC R/W-0, HSC R/W-0, HSC
IPL2
(
)
IPL1
IPL0
)
RA
N
OV
Z
C
bit 7
bit 0
Legend:
HSC = Hardware Settable/Clearable bit
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 15-9
Unimplemented:
Read as ‘
0
’
bit 8
DC:
ALU Half Carry/Borrow bit
1
= A carry-out from the 4
th
low-order bit (for byte-sized data) or 8
th
low-order bit (for word-sized data)
of the result occurred
0
= No carry-out from the 4
th
or 8
th
low-order bit of the result has occurred
bit 7-5
IPL<2:0>:
CPU Interrupt Priority Level Status bits
111
= CPU Interrupt Priority Level is 7 (15); user interrupts are disabled
110
= CPU Interrupt Priority Level is 6 (14)
101
= CPU Interrupt Priority Level is 5 (13)
100
= CPU Interrupt Priority Level is 4 (12)
011
= CPU Interrupt Priority Level is 3 (11)
010
= CPU Interrupt Priority Level is 2 (10)
001
= CPU Interrupt Priority Level is 1 (9)
000
= CPU Interrupt Priority Level is 0 (8)
bit 4
RA:
REPEAT
Loop Active bit
1
=
REPEAT
loop in progress
0
=
REPEAT
loop not in progress
bit 3
N:
ALU Negative bit
1
= Result was negative
0
= Result was non-negative (zero or positive)
bit 2
OV:
ALU Overflow bit
1
= Overflow occurred for signed (2’s complement) arithmetic in this arithmetic operation
0
= No overflow has occurred
bit 1
Z:
ALU Zero bit
1
= An operation, which effects the Z bit, has set it at some time in the past
0
= The most recent operation, which effects the Z bit, has cleared it (i.e., a non-zero result)
bit 0
C:
ALU Carry/Borrow bit
1
= A carry-out from the Most Significant bit (MSb) of the result occurred
0
= No carry-out from the Most Significant bit (MSb) of the result occurred
Note 1:
The IPLx Status bits are read-only when NSTDIS (INTCON1<15>) =
1
.
2:
The IPL<2:0> Status bits are concatenated with the IPL3 bit (CORCON<3>) to form the CPU Interrupt
Priority Level (IPL). The value in parentheses indicates the IPL when IPL3 =
1
.
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