Intel 2920 Design Handbook page 126

BANDWIDTH vs" PROGRAM LENGTH
Program Length
Sample" Signal""
Inst. % Rate 3dB Bandwidth
192 100 13kHz 43kHz
152 79 16kHz 53kHz
116
60 22kHz
73kHz
76
40
32kHz 107kHz
40 21 62kHz 207kHz
·Assumes 10MHz clock rate Sample rate = (;' Ins!
)(4~
x 10 9)HZ
··Assume BW3dB
'/J
(Sample rate)
BANDWIDTH
Nominally DC to 10kHz.
Signals up to 15kHz.
For higher complexity and bandwidth, 2920's can be
cascaded or operated In parallel.
Seed cr(program Len g th)-1
=..!..
p Device L
Complexity
a:
Program Length x
(#
Devices)
=
L x n
Performance
a:
Speed x Complexity
=
n
EVALUATING A POTENTIAL APPLICATION
Customer: Word description of application.
Block diagram.
Break block diagram down further into basic 2920
functional blocks.
FAE: Determine number of instructions and RAM loca·
tlons needed for these blocks and sum them up.
- Will It fit In the 2920?
- Will the resulting bandwidth meet
requirements?
- Can the 2920 meet other requirements, such
as dynamic range and I/O?
APPENDIX
A-3
The number of instructions, and the clock rate, will
determine the sample rate, and hence the signal bandwidth for
a given 2920 application. Because of the restriction on the
placement of the EOP instruction, program lengths will always
be a multiple of 4. A typical program length of from 80 to 192
instructions will yield a bandwidth in the range of DC·10kHz.
The shorter a 2920 program is, the higher the bandwidth
which can be handled. The minimum length for a 2920 program
is constrained by the I/O required. A full 9 bit input/output
sequence will require approximately 48 instructions, yielding a
sample rate of 52.1 kHz, and hence a bandWidth of approxi·
mately 17kHz. If dynamic range requirements are not too
strict, the input conversion sequence can be shortened by
reducing the number of bits converted, and bandwidths up to
approximately 20 kHz can be achieved.
For high complexity programs with high sample rates,
2920's can be cascaded (I/O requirements will result in a
minimum of about 48 instructions per device) or operated in
parallel. For example, if two 2920's are cascaded and each is
programmed to 50 percent of the maximum program length,
each devtce will be sampling at 26kHz, yet a full 192 instruc-
tion program is being executed.