Microchip Technology AC164139 Data Sheet
PIC24FJ256DA210 FAMILY
DS39969B-page 42
2010 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
(1)
R/W-0, HSC
(1)
R/W-0, HSC
(1)
R-0, HSC R/W-0, HSC R/W-0, HSC R/W-0, HSC R/W-0, HSC
IPL2
(2)
IPL1
(2)
IPL0
(2)
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
(1,2)
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 not 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 affects the Z bit, has set it at some time in the past
0
= The most recent operation, which affects the Z bit, has cleared it (i.e., a non-zero result)
bit 0
C: ALU Carry/Borrow bit
1
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 1:
The IPL Status bits are read-only when NSTDIS (INTCON1<15>) = 1.
2:
The IPL Status bits are concatenated with the IPL3 (CORCON<3>) bit to form the CPU Interrupt Priority
Level (IPL). The value in parentheses indicates the IPL when IPL3 = 1.
Level (IPL). The value in parentheses indicates the IPL when IPL3 = 1.