Datasheet
2013-2014 Microchip Technology Inc. DS70000689D-page 31
dsPIC33EPXXXGM3XX/6XX/7XX
3.6 CPU Control Registers
REGISTER 3-1: SR: CPU STATUS REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/C-0 R/C-0 R-0 R/W-0
OA OB SA
(3)
SB
(3)
OAB SAB DA DC
bit 15 bit 8
R/W-0
(2)
R/W-0
(2)
R/W-0
(2)
R-0 R/W-0 R/W-0 R/W-0 R/W-0
IPL2
(1)
IPL1
(1)
IPL0
(1)
RA N OV Z C
bit 7 bit 0
Legend: C = 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 OA: Accumulator A Overflow Status bit
1 = Accumulator A has overflowed
0 = Accumulator A has not overflowed
bit 14 OB: Accumulator B Overflow Status bit
1 = Accumulator B has overflowed
0 = Accumulator B has not overflowed
bit 13 SA: Accumulator A Saturation ‘Sticky’ Status bit
(3)
1 = Accumulator A is saturated or has been saturated at some time
0 = Accumulator A is not saturated
bit 12 SB: Accumulator B Saturation ‘Sticky’ Status bit
(3)
1 = Accumulator B is saturated or has been saturated at some time
0 = Accumulator B is not saturated
bit 11 OAB: OA || OB Combined Accumulator Overflow Status bit
1 = Accumulator A or B has overflowed
0 = Neither Accumulator A or B has overflowed
bit 10 SAB: SA || SB Combined Accumulator ‘Sticky’ Status bit
1 = Accumulator A or B is saturated or has been saturated at some time
0 = Neither Accumulator A or B is saturated
bit 9 DA: DO Loop Active bit
1 = DO loop in progress
0 = DO loop not in progress
bit 8 DC: MCU ALU Half Carry/Borrow
bit
1 = A carry-out from the 4th low-order bit (for byte-sized data) or 8th low-order bit (for word-sized data)
of the result occurred
0 = No carry-out from the 4th low-order bit (for byte-sized data) or 8th low-order bit (for word-sized
data) of the result occurred
Note 1: The IPL<2:0> bits are concatenated with the IPL<3> bit (CORCON<3>) to form the CPU Interrupt Priority
Level. The value in parentheses indicates the IPL, if IPL<3> = 1. User interrupts are disabled when
IPL<3> = 1.
2: The IPL<2:0> Status bits are read-only when the NSTDIS bit (INTCON1<15>) = 1.
3: A data write to the SR register can modify the SA and SB bits by either a data write to SA and SB or by
clearing the SAB bit. To avoid a possible SA or SB bit write race condition, the SA and SB bits should not
be modified using bit operations.