PDSP16256/A
Programmable FIR Filter
Supersedes version DS3709 5.1 January 1998
DS3709 - 6.0 August 1998
The PDSP16256 contains sixteen multiplier -
accumulators, which can be multi cycled to provide from 16 to
128 stages of digital filtering. Input data and coefficients are
both represented by 16-bit two’s complement numbers with
coefficients converted internally to 12 bits and the results
being accumulated up to 32 bits.
In 16-tap mode the device samples data at the system
clock rate of up to 25MHz. If a lower sample rate is acceptable
then the number of stages can be increased in powers of two
up to a maximum of 128. Each time the number of stages is
doubled, the sample clock rate must be halved with respect to
the system clock. With 128 stages the sample clock is
therefore one eighth of the system clock.
In all speed modes devices can be cascaded to provide
filters of any length, only limited by the possibility of
accumulator overflow. The 32-bit results are passed between
cascaded devices without any intermediate scaling and
subsequent loss of precision.
The device can be configured as either one long filter or
two separate filters with half the number of taps in each. Both
networks can have independent inputs and outputs.
Both single and cascaded devices can be operated in
decimate-by-two mode. The output rate is then half the input
rate, but twice the number of stages are possible at a given
sample rate. A single device with a 20MHz clock would then,
for example, provide a 128-stage low pass filter, with a 5MHz
input rate and 2·5MHz output rate.
Coefficients are stored internally and can be down loaded
from a host system or an EPROM. The latter requires no
additional support, and is used in stand alone applications. A
full set of coefficients is then automatically loaded at power on,
or at the request of the system. A single EPROM can be used
to provide coefficients for up to 16 devices.
EPROM
ADDR DATA
CHANGE
COEFF
POWER-ON
RESET
RES
INPUT
DATA
PDSP
16256
EPROM
SCLK
GND
OUTPUT
DATA
Fig. 1 A dual filter application
EPROM
ADDR DATA
CHANGE
COEFF
POWER-ON
RESET
RES
COEFFICIENTS
PDSP
16256
ANALOG
INPUT
ADC
EPROM
CLKOP
SCLK
GND
OUTPUT
DATA
FEATURES
s
Sixteen MACs in a Single Device
s
Basic Mode is 16-Tap Filter at up to 25MHz
Sample Rates
s
Programmable to give up to 128 Taps with
Sampling Rates Proportionally Reducing to 3·125MHz
s
16-bit Data and 32-bit Accumulators
s
Can be configured as One Long Filter or Two Half-
Length Filters
s
Decimate-by-two Option will Double the Filter Length
s
Coefficients supplied from Host System or local EPROM
APPLICATIONS
s
High Performance Digital Filters
s
Pulse Compression for Radar and Sonar
s
Matrix Multiplication
s
Correlation
Fig. 2 Typical system application
ASSOCIATED PRODUCTS
PDSP16350
I/Q Splitter/NCO
PDSP16510A
FFT Processor
ORDERING INFORMATION
Commercial (0
°
C to
170
°
C)
PDSP16256A/C0/AC
25MHz, PGA package
Industrial (240
°
C to
185
°
C)
PDSP16256 B0/AC
20MHz, PGA package
PDSP16256 B0/GC
20MHz, QFP package
Military (255
°
C to
1125
°
C)
PDSP16256 MA/ACBR 20MHz, MIL-STD-883*
(latest revision), PGA package
PDSP16256 MA/GCPR 20MHz, MIL-STD-883*
(latest revision), QFP package
*See
notes following Electrical Characteristics for further
information on MIL-STD-883 screening
MITEL [ MITEL NETWORKS CORPORATION ]
