6.2.17 CPU STATUS Register⁽¹⁾

Note:

The CPU STATUS register is not memory-mapped.

Table 6-17. Register Bit Attribute Legend
Symbol	Description	Symbol	Description	Symbol	Description
R	Readable bit	HC	Cleared by Hardware	(Gray cell)	Unimplemented
W	Writable bit	HS	Set by Hardware	X	Bit is unknown at Reset
C	Write to clear	S	Software settable bit	x	Channel number

Name:

SR


Bit	31	30	29	28	27	26	25	24

Access
Reset


Bit	23	22	21	20	19	18	17	16
	VF					CTX[2:0]
Access	R					R	R	R
Reset	0					0	0	0


Bit	15	14	13	12	11	10	9	8
	OA	OB	SA	SB	OAB	SAB		IPL3
Access	R/W	R/W	R/W	R/W	R	R/C		R/C
Reset	0	0	0	0	0	0		0


Bit	7	6	5	4	3	2	1	0
	IPL[2:0]			RA	N	OV	Z	C
Access	R/W	R/W	R/W	R	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0

Bit 23 – VF Vector (Fetch) Fail Status bit

Value	Description
`1`	Indicates to the bus error handler that the source of the bus error is a vector fetch. The vector data read will be substituted with the contents of the Vector Fail Address (VFA) SFR.
`0`	Indicates to the bus error handler that the source of the bus error is not a vector fetch.

Bits 18:16 – CTX[2:0] Current (W register) Context Identifier bits

Value	Description
111	Context 7 is currently in use
110	Context 6 is currently in use
101	Context 5 is currently in use
100	Context 4 is currently in use
011	Context 3 is currently in use
010	Context 2 is currently in use
001	Context 1 is currently in use
000	Context 0 is currently in use

Bit 15 – OA Accumulator A Fractional Overflow Status bit

Value	Description
`1`	Accumulator A fractional overflow has occurred (its contents can no longer be represented as a 1.31 fractional value)
`0`	Accumulator A not overflowed

Bit 14 – OB Accumulator B Fractional Overflow Status bit

Value	Description
`1`	Accumulator B fractional overflow has occurred (its contents can no longer be represented as a 1.31 fractional value)
`0`	Accumulator B not overflowed

Bit 13 – SA Accumulator A Saturation/Sign Overflow ‘Sticky’ Status bit

Value	Description
`1`	Accumulator A is saturated, or has been saturated at some time, or has overflowed into bit 71 (if saturation is disabled)
`0`	Accumulator A is not saturated or has not overflowed into bit 71 (if saturation is disabled)

Bit 12 – SB Accumulator B Saturation/Sign Overflow ‘Sticky’ Status bit

Value	Description
`1`	Accumulator B is saturated, or has been saturated at some time, or has overflowed into bit 71 (if saturation is disabled)
`0`	Accumulator B is not saturated or has not overflowed into bit 71 (if saturation is disabled)

Bit 11 – OAB OA || OB Combined Accumulator Fractional Overflow Status bit

Value	Description
`1`	Accumulators A or B fractional overflow has occurred (one or both of their contents can no longer be represented as a 1.31 fractional value)
`0`	Neither Accumulators A nor B have overflowed

Bit 10 – SAB SA || SB Combined Accumulator ‘Sticky’ Status bit

Value	Description
`1`	Accumulators A or B are saturated, or have been saturated at some time, or have overflowed into bit 71 (if saturation is disabled)
`0`	Neither Accumulator A nor B are saturated or have overflowed into bit 71 (if saturation is disabled)

Bit 8 – IPL3 MS-bit of CPU Priority Level Nibble bit

Value	Description
1	CPU Priority ≥ 8 (trap exception underway)
0	CPU Priority < 8 (no trap exception underway)

Bits 7:5 – IPL[2:0] CPU Interrupt Priority Level status bits

User Mode: This bit is R/C-0 (read only if Supervisor Mode supported) and will reset to 1’b0.

Supervisor Mode: This bit is R/C-0 (CPU will reset into Supervisor Mode).

Value	Description
111	All interrupts disabled
110	Level 7 interrupts enabled
101	Level 6 and 7 interrupts enabled
100	Level 5 through 7 interrupts enabled
011	Level 4 through 7 interrupts enabled
010	Level 3 through 7 interrupts enabled
001	Level 2 through 7 interrupts enabled
000	Level 1 through 7 interrupts enabled

Bit 4 – RA REPEAT Loop Active bit

Value	Description
1	REPEAT loop in progress
0	REPEAT loop not in progress

Bit 3 – N ALU Negative bit

Bit 2 – OV ALU Overflow bit

Bit 1 – Z ALU ‘Sticky’ Zero bit

Value	Description
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

SR[31:0] is stacked during exception processing, preserving context.

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