
Using the Parallel Port
8-18
ADSP-2126x SHARC Processor Hardware Reference
over core driven transfers is that the core can continue executing code
while sequential data is imported/exported in the background.
Unlike the external port on previous SHARC processors, the ADSP-2126x
core cannot directly access the external parallel bus. Instead, the core ini-
tializes two registers to indicate the external address and address-modifier
and then accesses data through intermediate registers. Then, when the
core accesses either the
PPTX
or
PPRX
registers, the parallel port
writes/fetches data to/from the specified external address. The details of
this functionality and the four main techniques to manage each transfer
are detailed below. In general, core-driven transfers are most advantageous
when performing single-word accesses and/or accesses to non-sequential
addresses.
DMA Transfers
To use the parallel port for DMA programs, start by setting up values in
the DMA parameter registers. The program then writes to the
PPCTL
regis-
ter to enable
PPDEN
with all of the necessary settings like cycle duration
value, transfer direction, and so on. While a parallel port DMA is active,
the DMA parameter registers are not writable. Furthermore, only the
PPEN
and
DMAEN
bits (in the
PPCTL
register) can be changed. If any other bit is
changed, the parallel port will malfunction. It is recommended that both
the
PPDEN
and
PPEN
bits be set and reset together to ensure proper DMA
operation.
To see an example program that sets up a parallel port DMA, see
Core Driven Transfers
Core-driven transfers can be managed using four techniques. The transfers
can 1) use interrupts, 2) poll status bits in the
PPCTL
register, 3) predict
when each access will complete by calculating the data and
ALE
cycle dura-
tions, or 4) rely on the fact that the core stalls on certain accesses to
PPRX
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 ...