deciphering EPROM data - Page 1
Forum section: electronics / testgear

author: tmg
author_rank: Newbie
timestamp: May 07, 2013, 04:41:43 pm
content: So I have a EPROM out of an RF power detector that i am trying to edit the data on. I have the a printout of the end result of what the data on the EPROM produces and i have the binary at all the addresses of the EPROM (most on which are empty). But i can't figure out how to convert the binary into anything sensible. Any ideas?Detailed Info:EPROM PN: CY7C291ADatasheet:http://components.arrow.com/part/dataview/129890S1042298N5453Data derived from EPROM:(I got these by feeding in each address into the address bus and reading the output with an arduino mega)QuoteEPROM Binary valuesQuote

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 07, 2013, 05:25:45 pm
content: I doubt that the EPROM data you posted is correct, what are the odds that bit0 and bit2 are always zero, and bit1 is 1 only once?And how exactly did you get what you call data derived from EPROM?

author: kfitch42
author_rank: Frequent Contributor
timestamp: May 07, 2013, 05:36:03 pm
content: Quote from: PA0PBZ on May 07, 2013, 05:25:45 pmAnd bit 3 is set only thrice.Is the data extraction repeatable? Check for loose connections.The best approach (once you can reliably/repeatably extract the data) would be to try mucking a bit somewhere and see what changes in that report.

author: kfitch42
author_rank: Frequent Contributor
timestamp: May 07, 2013, 05:48:52 pm
content: QuoteYou only showed us 1K of data.This is an EPROM, not an EEPROM. Do you have a windowed package? I think this guy can only be reprogrammed after getting UV exposed to erase.

author: tmg
author_rank: Newbie
timestamp: May 07, 2013, 06:53:27 pm
content: QuoteIt is highly possible that i am doing this all wrong, this is my 1st adventure with an EPROM.I dont have a proper EPROM programmer so am trying to hack one together with an arduinoi hooked up all the address lines to outputs from the microcontroller and i am reading the output inI turn the enable pins on and just count up in binary recording the output.QuoteYes

author: kfitch42
author_rank: Frequent Contributor
timestamp: May 07, 2013, 07:24:02 pm
content: Quote from: tmg on May 07, 2013, 06:53:27 pmReading the EPROM from an Arduino should be doable. Writing to it will be much tougher.Note that you will need 12V on /CS1 to program. Also from the datasheet:QuoteI suspect you will be better off buying an actual programmer. Just check that it supports your chip. I did a quick check and I don't think the one Dave reviewed recently supports your chip.

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 07, 2013, 07:27:20 pm
content: At first: you can't change the values in the EPROM without erasing (with UV) and reprogramming the device, so editing the data is not that easy.Then, you list the contents of the EPROM twice, the first table is readable text and the second one contains values. What is the difference?Maybe it would be a bit easier to give you advice if you can tell what model of RF power detector you are working on and what you are trying to do. A picture of the PCB would help also.

author: tmg
author_rank: Newbie
timestamp: May 07, 2013, 07:37:14 pm
content: At the moment all i want to do i read it and figure out how it is encoded. Basically i want to be fairly certain that i will be able to know what to write to the chip should i get a proper programmer.QuoteThe 1st data the text is what i read off the machine's display when it is reading the rom. the 2nd, all binary is what i can read off the chipi am trying to figure out what addresses on the chip relate to what data.Ideally i would find an eeprom that i could replace this on with but i haven't started that search yet b/c it is pointless if i dont know what the data means

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 07, 2013, 07:41:17 pm
content: Something doesn't make sense (yet).If the calibration data is in the EPROM there is no easy way to recalibrate the device.What else is in the RF detector, is there also an EEPROM maybe?

author: free_electron
author_rank: Super Contributor
timestamp: May 07, 2013, 07:48:05 pm
content: you don't recalibrate these things. the only time recalibration is need is if the thermistors in the bolometer have been altered. as this is an undoable thing unless you have wirebonders this calibration is useless.This is factory work. They measure the device , calculate compensation values for the meter and store this in the eeprom. There may not even be a direct relation between the printed table on the unit and what is stored in the rom.why do you want to play with this ?

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 07, 2013, 07:52:39 pm
content: Quote from: free_electron on May 07, 2013, 07:48:05 pmI agree, but since it lists both the calibration date and says "factory calibration" it makes me wonder. Why are you so sure it is bolometer based?QuoteYes, that is what I tried to ask.

author: free_electron
author_rank: Super Contributor
timestamp: May 07, 2013, 08:05:43 pm
content: Quote from: PA0PBZ on May 07, 2013, 07:52:39 pmcause most of the agilents are bolometer based.... his list shows two diode resistances ...maybe tha rom sits in a socket and is swappable by the callabs. they would then have a piece of software that alters the infor , writes a new rom , tech swaps roms and puts cover back on.or , if the probe is being repaired in a service center thise guys would write new prom and it would not say factory but 'refurbished' . that way you know it has been reworked.educated speculation on my part ...

author: bilko
author_rank: Frequent Contributor
timestamp: May 07, 2013, 08:33:25 pm
content: Once you have managed to retrieve the data from the EPROM you can copy it to a NVRAM. I'm sure that you will find a chip that has the same address and data lines. Just hook up a battery backup supply and you can switch between your gear and the arduino rig, no need to Erase and reprogram EPROMS. I have done this in the past, a long time ago and it works without any problems.

author: tmg
author_rank: Newbie
timestamp: May 08, 2013, 12:23:34 pm
content: QuoteThis is precisely it, but i cant get the device that programs the proms anymore. It was an extension of the power meter and you program it by typing into the meter.So the old way the meter and extension would encode the data for you onto a new prom.The Sensor is a gigatronics 16000 something (1693? i dont have it in front of me right now).QuoteThis sensor is diode based and the mfr flyer says PROM and diode detectors are field replaceable.http://www.gigatronics.com/uploads/document/8500A-Series-Power-Meter-Datasheet.pdfQuoteBecause I have some sensors that read very close to nominal when you force the offset to be zero, by selecting a freq of 1GHz regardless of input, but when you specify the frequency and it applies the offset for that freq. the reading its sufficiently off.Quoteif it is non-volatile why the need to batt. backup. which wont work for me b/c these sensors can spend alot of time unplugged.

author: kfitch42
author_rank: Frequent Contributor
timestamp: May 08, 2013, 03:41:34 pm
content: Quoteif it is non-volatile why the need to batt. backup. which wont work for me b/c these sensors can spend alot of time unplugged.It is somewhat common for test equipment to store cal data in SRAM with a battery backup connected to the SRAM, which can last years. Maintaining data is SRAM doesn't take much power. You can search around this forum and find numerous threads about changing batteries in benchtop multimeters.As I understand it a 'true' NVSRAM essentially contains an internal battery, with a specified lifetime (e.g. 10 years).I am guessing there isn't much room inside the power sensor to make a mod like adding a battery. Guess you could just duck tape it on the outsideGetting a pin compatible (NV)SRAM is probably going to be necessary, at least for figuring this guy out. The datasheet on your EPROM suggests a 35minute erase time. Trying out different tweaks to the data might be quite painful if it takes close to an hour to tweak a bit and try it out.What speed grade is your chip? The data sheet lists 20ns, 25ns, 35ns, and 50ns variants. A quick parametric search on digikey suggests that getting 20ns or faster severely limits your options.