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PICList Thread
'[EE]:Syllabic Integrator'
2000\11\11@194656 by Jinx

face picon face
Can someone please explain estimate and syllabic integrators. I've
looked around and keep coming up with the same three very similar
web pages eg

I'd like to replace a DSP chip that performs CVSD  (Continuously
Variable Slope Delta) functions for converting waves to SRAM data.
The block diagram of the chip's input section shows the 10-bit ADC,
comparator, estimate integrator, and syllabic integrator. The output
is an adder + 10-bit DAC

The chip produces a stream of 1-bit differences between samples
on audio range frequencies at 64k samples/sec. Is it possible to do
this in s/w (with external ADC/DAC) ? I like what the chip does and
would want to keep the same specs

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2000\11\11@201223 by Bob Ammerman

picon face
Hey, I've got the same problem. A system that contains a CVSD chip that has
been obsoleted.
I'm wondering if it is possible to do CVSD in firmware on a PIC.

Does anybody know of a software implementation of CVSD on any platform
whatsoever for which I can obtain the source code?

Or a detailed description of the algorithm?

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level

{Original Message removed}

2000\11\12@041009 by Chris Carr

I note that CML are producing a
full duplex CVSD Codec  part number CMX639
there is also the FX619 intended for Military Comms

Woops the alarm bell have just gone off at Menwith Hill :-)


{Original Message removed}

2000\11\12@055157 by Jinx

face picon face
> I note that CML are producing a
> full duplex CVSD Codec  part number CMX639
> there is also the FX619 intended for Military Comms

> Chris

These seem to be like memoryless ISD chips. I'm looking at an
app right now that could use ISDs or the CML parts. Plus for the
CML parts is that memory size is infinite whereas AFAIK you can't
hook up external memory to ISDs. Minor glitch might be the memory
chip availability situation but wouldn't pooh-pooh the CML altogether
for future consideration, I'll get a price on them at least. Big downer
is the bandwidth, only 4kHz, despite CML sampling at up to 128kbs.
The one I use now has a bandwidth of 18kHz, around about cassette
tape quality, which I need for good music sampling

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2000\11\12@121918 by Nikolai Golovchenko

Here is a description of CSVD:

It's not very detailed, but gives an idea.

At 64 kbit/s for a 20Mhz PIC with ADC this is 78
instructions, which is a lot. It probably can also run
demodulation, using PORTB and some resistors as a DAC.

ADC should be fast enough though: 15.625 us/sample. I just
looked in the data sheet - it says that PIC16F87x ADC takes
at least 1.6 us per bit. Together with sample aquisition
time and other stuff we can get only about 6 bits in that
time. For a good quality audio this is probably too small,
even at 64 kHz.

But 32 kbit/s CVSD looks possible with a PIC16F87x (using
full 10 bit resolution of its ADC).


---- Original Message ----
From: Bob Ammerman <RAMMERMANspamKILLspamPRODIGY.NET>
Sent: Sunday, November 12, 2000 3:00:56
 To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
Subj: [EE]:Syllabic Integrator

{Quote hidden}

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2000\11\12@125917 by rottosen

See the specifications for the Motorola MC3417, MC3418 or MC34115 for a
simple block diagram af an analog version of CVSD. Or here is an
application note with the same information:  (About 370K in size).

Many(!) years ago I did an implemention of this using a 6502 series
processor with external ADC and DAC. I was able to record several
seconds of audio as I remember.

-- Rich

Jinx wrote:
{Quote hidden}

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2000\11\12@131359 by rottosen


See my other message referring to the Motorola analog parts.

I don't have the software readily available. (It was a long time ago on
an Apple ][). The basic idea is that you A/D convert the audio then
compare it in software to the output of a counter used to approximate
the "leaky" integrator. The integrator is driven from the 3 or 4 bit
shift register implemented as shown in the block diagram for the

I did a direct translation of the hardware to software without any
clever tricks needed. This shouldn't be hard to implement with a
PIC12C671 and an external DAC. Since the data rate is low, the DAC can
probably be a PWM type. One of the neat things about CVSD is that it is
very highly oversampled by its very nature. This makes anti-aliasing
filters easier.

If this isn't enough help, I can try to find the old 6502 software.

-- Rich

Bob Ammerman wrote:
{Quote hidden}

> {Original Message removed}

2000\11\13@134129 by rottosen

part 0 44 bytes
his is a multi-part message in MIME format.
part 1 3159 bytes content-type:text/plain; charset=us-ascii (decoded 7bit)


Now you went and done it. :-)

I fired up my old Apple ][ (that's an oxymoron) and pulled off the CVSD
files. I have attached them in a zip file. Use them at your own risk
since I haven't looked at them in a dozen years. They are in a slightly
unusual (for the 6502 microprocessor) assembler syntax. I think you can
figure it out though. Wow, is this a test of how well I commented code
or what?

If you have any questions I will try to answer them out of the dust
covered corners of my brain.

-- Rich

Bob Ammerman wrote:
{Quote hidden}

part 2 4714 bytes content-type:application/x-zip-compressed; (decode)

part 3 228 bytes
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