Using Computational Status
2-16
ADSP-2126x SHARC Processor Hardware Reference
Though these rounding modes comply with standards set for float-
ing-point data, they also apply for fixed-point multiplier operations on
fractional data. The same two rounding modes are supported, but only the
round-to-nearest operation is actually performed by the multiplier. Using
its local result register for fixed-point operations, the multiplier
rounds-to-zero by reading only the upper bits of the result and discarding
the lower bits.
Using Computational Status
The multiplier and ALU each provide exception information when exe-
cuting floating-point operations. Each unit updates overflow, underflow,
and invalid operation flags in the processing element’s arithmetic status
(
ASTATx
and
ASTATy
) registers and sticky status (
STKYx
and
STKYy
) registers.
An underflow, overflow, or invalid operation from any unit also generates
a maskable interrupt. There are three ways to use floating-point excep-
tions from computations in program sequencing:
• Interrupts. Enable interrupts and use an interrupt service routine
(ISR) to handle the exception condition immediately. This method
is appropriate if it is important to correct all exceptions as they
occur.
• The
ASTATx
and
ASTATy
registers. Use conditional instructions to
test the exception flags in the
ASTATx
or
ASTATy
registers after the
instruction executes. This method permits monitoring each
instruction’s outcome.
• The
STKYx
and
STKYy
registers. Use the bit test (
BTST
) instruction
to examine exception flags in the
STKY
register after a series of oper-
ations. If any flags are set, some of the results are incorrect. This
method is useful when exception handling is not critical.
Содержание ADSP-21261 SHARC
Страница 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Страница 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Страница 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Страница 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Страница 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...