Parallel Port Operation
8-6
ADSP-2126x SHARC Processor Hardware Reference
In a read cycle, the
WR
and
ALE
signals are inactive and
RD
is strobed. If the
upper 16 bits of the external address have changed, this cycle is always pre-
ceded by an
ALE
cycle. In 8-bit mode, the lower 8 bits of the address,
EA7–
0
, are driven on the
AD15–8
pins, and data is sampled from the
AD7–0
pins
on the rising edge of
RD
. In 16-bit mode, address bits are not driven in the
read cycle, the external address is provided entirely by the external latch,
and data is sampled from the
AD15–0
pins at the rising edge of
RD
. Read
cycles can be lengthened by configuring the parallel port data cycle dura-
tion bits in the
PPCTL
register.
In a write cycle,
RD
and
ALE
are inactive and
WR
is strobed. If the upper 16
bits of the external address have changed, this cycle is always preceded by
an
ALE
cycle. In 8-bit mode, the lower 8 bits of the address are driven on
the
AD15–8
pins and data is driven on the
AD7–0
pins. In 16-bit mode,
address bits are not driven in the write cycle, the external address is pro-
vided entirely by the external latch, 16-bit data is driven onto the
AD15-0
pins, and data is written to the external device on the rising edge of the
WR
signal. Address and data are driven before the falling edge of
WR
and deas-
serted after the rising edge to ensure enough setup and hold time with
respect to the
WR
signal. Write cycles can be lengthened by configuring the
parallel port data cycle duration bits in the
PPCTL
register.
Reading From an External Device or Memory
The parallel port has a two stage data FIFO for receiving data (
RXPP
). In
the first stage, a 32-bit register (
PPSI
) provides an interface to the external
data pins and packs the 8- or 16-bit data into 32 bits. Once the 32-bit
data is received in
PPSI
, the data is transferred into the second 32-bit reg-
ister (
RXPP
). Once the receive FIFO is full, the chip cannot initiate any
more external data transfers. The
RXPP
register acts as the interface to the
core or I/O processor (for DMA).
The
PPTRAN
bit must be zero in order to be read.
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 ...