
ADSP-2126x SHARC Processor Hardware Reference
8-21
Parallel Port
TXPP
occurs on the external bus. For example, after the core reads the
PPTX
register, it will take some number N core-cycles for the PP to shift out that
data to the memory. During that time, the core can go on doing other
tasks. After N core-cycles have passed, the parallel port may be disabled
and the external address register updated for another access.
To determine the duration for each access, the designer simply add's the
number of data-cycles and the duration of each (measured in
CCLK
cycles)
along with the number of
ALE
cycles (which are fixed at 3
CCLK
cycles).
This duration is deterministic, and is based on two settings in the
PPCTL
register—parallel port data-cycle duration (
PPDUR
) and Bus Hold Cycle
Enable (
PPBHC
).
Please refer to
for further explanation of the par-
allel port bus cycles, but in summary, programs can use the following
values:
• each
ALE
cycle is fixed at 3
CCLK
cycles, regardless of the
PPDUR
or
PPBHC
settings.
• each Data cycle is the setting in the
PPDUR
register (+1 if
PPBHC
=1)
For example, in 8-bit mode, a single-word transfer is comprised of 1
ALE
cycle and 4 Data cycles. If
PPDUR3
is used (the fastest case) and
PPBHC
= 0, this transfer completes in:
(1
ALE
-cycle x 3
CCLK
) + (4 data-cycles x 3
CCLK
) = 15 core cycles per 32-bit
word.
This means that 15-instructions after data is written to
TXPP
or read from
RXPP
, the parallel port has finished writing/fetching that data externally,
and the parallel port may be disabled. This case is shown in
.
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 ...