Datasheet

dsPIC33EPXXX(GP/MC/MU)806/810/814 and PIC24EPXXX(GP/GU)810/814
DS70616F-page 42 Preliminary © 2009-2012 Microchip Technology Inc.
3.7 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
(1)
OB
(1)
SA
(1,4)
SB
(1,4)
OAB
(1)
SAB
(1)
DA
(1)
DC
bit 15 bit 8
R/W-0
(2,3)
R/W-0
(2,3)
R/W-0
(2,3)
R-0 R/W-0 R/W-0 R/W-0 R/W-0
IPL<2:0> RA N OV Z C
bit 7 bit 0
Legend: U = Unimplemented bit, read as ‘0’
R = Readable bit W = Writable bit C = Clearable bit
-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)
1 = Accumulator A has overflowed
0 = Accumulator A has not overflowed
bit 14 OB: Accumulator B Overflow Status bit
(1)
1 = Accumulator B has overflowed
0 = Accumulator B has not overflowed
bit 13 SA: Accumulator A Saturation ‘Sticky’ Status bit
(1,4)
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
(1,4)
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)
1 = Accumulators A or B have overflowed
0 = Neither Accumulators A or B have overflowed
bit 10 SAB: SA || SB Combined Accumulator ‘Sticky’ Status bit
(1)
1 = Accumulators A or B are saturated or have been saturated at some time
0 = Neither Accumulator A or B are saturated
bit 9 DA: DO Loop Active bit
(1)
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: This bit is available on dsPIC33EPXXX(GP/MC/MU)806/810/814 devices only.
2: 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.
3: The IPL<2:0> Status bits are read only when NSTDIS = 1 (INTCON1<15>).
4: 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.