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I'm about to buy a parallel ADC to connect to an EPROM in a analog-digital circuit. I've found some potential ADCs but am having trouble deciding if the ADC and EPROM are compatible.

A bistable multivibrator provides a sample signal to the ADC, so there needs to be an input pin to allow for this, which I can't identify. While most ADCs seem to do this without the two monostables, the point is to teach the function of these and the production of a digital signal.

The project is to update an undergraduate electronics project, where students build a digital thermometer, a lot of the currently used components are obsolete. The signal from a thermistor is converted by the ADC, which passes 8-bits to the EPROM. The EPROM outputs a temperature to a 7-segment display.

Components such as op-amps and multivibrators are used for teaching basic electronics (differential inputs, +ve to -ve triggering, A_D conversion, what a byte is etc.), so while there are easier options (we'd use an Arduino if we could), the project requires that we carry out the task this way.

Part of the project is evaluating different options, and as this is electrical engineering, it would be interesting to gauge your opinions on what constitutes basic electronics. What is important to teach absolute beginners and can it be done using microcontrollers?

Sorry if I've missed anything out or if the question seems vague. A lot of these concepts are new to me as a Physicist, and so far any components I look into seem impossible to understand. Most of my electronics knowledge is from carrying out this same experiment two years ago.

Specific issues:

So far I've identified 12 essential pins on the ADC. These are: - 8 output pins - Vin-, Vin+ - Voltage regulator signal (I think this is labelled as Vcc/Vref in the datasheet) - Signal from the multivibrators (unsure how this pin is labelled in the datasheet)

Is this correct?

Do you think the selected components are suitable for this task?

Datasheets for the two components:

ADC, EPROM

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    \$\begingroup\$ You say "digital->analog" therefore are you actually looking for DACs and not ADCs? \$\endgroup\$ – Andy aka Feb 24 '14 at 12:08
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    \$\begingroup\$ The two devices are electrically compatible, in the sense that they both have 5V TTL interfaces. But you're going to have to give us some idea of what you're trying to accomplish functionally in order to answer any question about compatibility at a higher level. \$\endgroup\$ – Dave Tweed Feb 24 '14 at 12:42
  • \$\begingroup\$ Apologies, I'm trying to order these within the next two days and everything's a bit frantic. It is an analogue->digital process, so an ADC is required. \$\endgroup\$ – user37704 Feb 24 '14 at 13:53
  • \$\begingroup\$ Sorry, I keep adding information without giving a full-picture of the situation. Edited the question to give more information. Thanks for your help though, hugely appreciated :) \$\endgroup\$ – user37704 Feb 24 '14 at 14:49
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To answer the specific question about triggering the ADC: If you're not using it with a microprocessor of some sort, you could simply tie the CS- and RD- lines low, which will permanently enable the parallel data outputs, and then pulse the WR- line low to initiate each conversion.

You'll get a pulse on the INTR- output when the conversion is complete. (Note that it won't latch as long as CS- and RD- are tied low.)

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  • \$\begingroup\$ Thanks, what does it mean to tie those lines low? \$\endgroup\$ – user37704 Feb 24 '14 at 14:56
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You have linked to a one-time programmable EPROM (basically a UV-erasable EPROM in a plastic package) and an 8-bit ADC. Thank you for that.

It cannot be used with the ADC without some kind of logic (usually supplied by a microcontroller) inbetween, unless you wish to simply index the pre-programmed EPROM with the ADC output.

Once the EPROM (it's really a PROM) is programmed, it cannot be erased electrically (or optically, since it's in an opaque package), so if you're trying to get a more-or-less permanent record, that's what that chip could do.

Please clarify the question.

Edit: As @Tut suggested, if your intention is to use the EPROM as a permanently programmed lookup table indexed by one or more ADCs, that would work. You could get one of four functions of two input variables by using two ADCs. The output of the ADC is electrically compatible with the address lines of the EPROM.

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  • \$\begingroup\$ I think the question needs to be clarified. Perhaps the OP wishes to use the EPROM as a look-up table for linearization or some type of distortion, in which case the outputs of the ADC would connect to (some of) the EPROM address lines. \$\endgroup\$ – Tut Feb 24 '14 at 12:47
  • \$\begingroup\$ @Tut That's an excellent point. I'll edit my answer accordingly, thanks. \$\endgroup\$ – Spehro Pefhany Feb 24 '14 at 12:50

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