Core Control Registers

Table 3-1. Status Register Description (Continued)

Name

Description

Settings

 

 

 

 

 

 

 

 

OVE

Overflow Exception Enable Bit

0

= Overflow exception generation is disabled

Bit 20

Enables or disables the generation of an

1

= Overflow exception generation is enabled, unless DOVF

 

exception caused by an overflow. The

 

bit in EMR is already 1

 

DOVF bit in EMR is always set when an

 

 

 

overflow occurs. If the OVE bit is set and

 

 

 

the DOVF bit is already set, no exception

 

 

 

is generated until the DOVF bit is cleared

 

 

 

and set again.

 

 

 

See Section 3.1.2, “Exception and Mode

 

 

 

Register (EMR),” for more information.

 

 

 

This bit is cleared at core reset.

 

 

 

 

 

 

DI

Disable Interrupts Bit — When this bit

0

= Interrupts enabled

Bit 19

is set, no maskable interrupts are

1

= Interrupts disabled

 

serviced, regardless of the IPL values,

 

 

 

which remain unchanged.

 

 

 

This bit can be set with the DI instruction,

 

 

 

which ensures that interrupts are

 

 

 

masked immediately, and can be cleared

 

 

 

with the EI instruction.

 

 

 

This bit is cleared at core reset.

 

 

 

 

 

 

EXP

Exception Mode Bit — Selects the

0

= Normal working mode, active SP is NSP

Bit 18

active stack pointer and working mode of

1

= Exception working mode, active SP is ESP

 

the core.

 

 

 

This bit is set at core reset.

 

 

 

 

 

 

R

Reserved

 

 

Bits

 

 

 

17–12

 

 

 

 

 

 

 

VF3–VF0

Viterbi Flags — Reflect the status of the

0

= Appropriate 16-bit portion transferred

Bits 11–8

two parallel conditional transfers in the

1

= Appropriate 16-bit portion not transferred

 

MAX2VIT instruction. These flags are

 

 

 

generally used in conjunction with the

 

 

 

VSL instructions. Two Viterbi flags can

 

 

 

be independently set or cleared

 

 

 

according to the MAX2VIT result.

 

 

 

For more information, see MAX2VIT and

 

 

 

VSL in Appendix A, “SC140 DSP Core

 

 

 

Instruction Set.”

 

 

 

These bits are cleared at core reset.

 

 

RReserved

Bit 7

3-4

SC140 DSP Core Reference Manual

Page 104
Image 104
Freescale Semiconductor SC140 specifications Overflow Exception Enable Bit, Disable Interrupts Bit When this bit, Reserved