
Using the Parallel Port
8-20
ADSP-2126x SHARC Processor Hardware Reference
external byte address indicated by
EIPP
. Subsequently, additional data is
fetched only when the core reads (empties)
RXPP
.
The following are guidelines that programs must follow when the proces-
sor core accesses parallel port registers.
• While a DMA transfer is active, the core may only write the
PPEN
and
PPDEN
bits of
PPCTL
. Accessing any of the DMA parameter reg-
isters or other bits in
PPCTL
during an active transfer will cause the
parallel port to malfunction.
• Core reads of the FIFO register during a DMA operation are
allowed but do not affect the status of the FIFO.
If
PPEN
is cleared while a transfer is underway (whether core or
DMA-driven), the current external bus cycle (
ALE
cycle or data
cycle) will complete but no further external bus cycles occur. Dis-
abling the parallel port clears the data in the
RXPP
and
TXPP
registers.
• Core reads and writes to the
TXPP
and
RXPP
registers update the sta-
tus of the FIFO when DMA is not active. This happens even when
the parallel port is disabled.
• The
PPCTL
register has a two-cycle effect-latency. This means that if
programs write to this register in cycle N, the new settings will not
be in effect until cycle N + 2. Avoid sampling
PPBS
until at least 2
cycles after the
PPEN
bit in
PPCTL
is set.
• For core-driven transfers over the parallel port, the
IIPP
,
IMPP
,
ICPP
, and
ECPP
registers are not used. Only the
EIPP
and
EMPP
regis-
ters need to be initialized before accessing the
TXPP
or
RXPP
buffers.
Known Duration Accesses
Of these methods, known duration accesses are the most efficient because
they allow the core to execute code while the transfer to/from the
RXPP
or
Summary of Contents for ADSP-21261 SHARC
Page 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Page 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Page 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Page 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Page 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Page 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Page 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Page 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Page 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Page 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Page 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Page 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...