ADSP-2126x SHARC Processor Hardware Reference
8-13
Parallel Port
access constraints (occurrence of
ALE
cycles at page boundaries, duration
of data cycles, and/or addition of hold time cycles).
The maximum parallel port speed is 1/3 of the core. The relationship
between core clock and parallel port speed is static. For a 200 MHz core
clock, the parallel port runs at 66 MHz. Since there is no parallel port
clock signal, it is easiest to think of parallel port throughput in terms of
core clock cycles.
As described in
“Parallel Port Operation” on page 8-5
, parallel port
accesses require both
ALE
cycles to latch the external address and addi-
tional data cycles to transmit or receive data. Therefore, the throughput
on the parallel port is determined by the duration and number of these
cycles per word. The duration of each type of cycle is shown below and the
frequency is determined by the external memory width.
There is one case where the frequency is also determined by the
external address modifier register (
EMPP
).
•
ALE
cycles are fixed at 3 core cycles (
CCLK
) and are not affected by
the
PPDUR
or
BHC
bit settings. In this case, the
ALE
is high for 2 core
clock cycles. Address for
ALE
is set up a half core clock cycle before
ALE
goes HIGH (active) and remains on bus a half cycle after
ALE
goes LOW (inactive). Therefore, the total
ALE
cycles on the bus are
1/2 + 2 + 1/2 = 3 core clock cycles. Please refer to the data sheet for
more precise timing characteristics.
• Data cycle duration is programmable with a range of 3 to 32
CCLK
cycles. They may range from 4 to 33 cycles if the
BHC
bit is set (=1).
The following sections show examples of transfers that demonstrate the
expected throughput for a given set of parameters. Each word transfer
sequence is made up of a number of data cycles and potentially one addi-
tional
ALE
cycle.
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 ...