Help needed identifying PDIP EEPROM - Page 1
Forum section: electronics / beginners

author: ESXi
author_rank: Regular Contributor
timestamp: April 17, 2018, 05:32:35 pm
content: Hello,I want to read a EEPROM chip, but I can't find the brand or datasheet.It is a "P95AD 93C46EN". The chips looks like this with also the "F" on it.(See the attached image of my chip)All the information I found was this;http://www.int-thinking.net/ic218914/93C46EN.htmlit says manutacturer NSC, this is not right? It's also not FairChild or Micro-something and so on?What I do know is that it is the same brand chip and same model number so it is a three-wire serial eeprom 1k.In the end I want to connect this to my Arduino and dump the eeprom and write it to a new one.

author: DC1MC
author_rank: Super Contributor
timestamp: April 17, 2018, 05:38:51 pm
content: It's a Microwire EEPROM, a bastard child protocol between SPI and I2Chttp://ww1.microchip.com/downloads/en/devicedoc/21712B.pdfRead/Write it with this stuff:https://github.com/tim0s/MicrowireEEPROMGood luck,DC1MC

author: ESXi
author_rank: Regular Contributor
timestamp: April 17, 2018, 05:57:32 pm
content: Hey Thanks DC1MC!I will post pictures here when I finished all the work. My speedometer failed today in my car (earlier replaced the sensor in the transmission) but today the stepper motor gave the ghostand had to buy a "new used" mileage clock. Hopefully I can restore it with original mileage..I did a continuity test on the stepper motor, the last contacts in the motor almost at the end are crunchy as f. The pointer stays between 0 and 2 and it's tripping when I power up the dashboard. It's a old VW 3.

author: amyk
author_rank: Super Contributor
timestamp: April 18, 2018, 01:31:16 am
content: It is Fairchild (now ON), part is FM93C46EN. Non-RoHS and very old, obsolete part.

author: drussell
author_rank: Super Contributor
timestamp: April 18, 2018, 01:46:24 am
content: The 93C46 is a bog-standard EEPROM, readily available in many different versions. Digikey alone returns 306 hits with 67 varieties in stock for immediate shipment...I can't see why you would have difficulty finding datasheets for them, they're a common part.

author: ESXi
author_rank: Regular Contributor
timestamp: April 19, 2018, 04:05:41 pm
content: Quote from: drussell on April 18, 2018, 01:46:24 amSome chips are easy to find and identify... Like when they have ST/AT on them and a part number that shows up in a search engine. I don't know nothing about other brands. For you the F is a easy and dead giveaway that it's a Fairchild jobby.I triedwww.alldatasheet.comwithout much luck because the numbers don't match up.Have looked at wikipedia for chip manufacturers brands under the letter F indeed found fairchild but not a datasheet using alldatasheet or google.I know the part is really old. It's out of a speedometer from a car that is almost 26 years old.It seems like all I had to do was to add 'FM' in front of the 93C46. Anyways I will cut the traces now on the PCB and I will try to read the eeprom in-circuit using a Arduino with MicrowireEEPROM lib from github which by the way looks promising.

author: ESXi
author_rank: Regular Contributor
timestamp: April 20, 2018, 05:47:32 pm
content: So yeah. I dumped the eeprom successfully, but I really don't understand the data structure(I dumped yesterday and today, so I have two dumps which show differences). I guess I will just have to place the eeprom over to it's new cluster and call it a day. Not sure how healthy this one is, but I guess they are all just old, also the used one I got (probably the same age).Got myself two dip 8 sockets so I can easily put the old one holding my mileage back to the ''new'' cluster.

author: DC1MC
author_rank: Super Contributor
timestamp: April 20, 2018, 09:22:49 pm
content: Quote from: ESXi on April 20, 2018, 05:47:32 pmIf you ever wanted to understand you data structure make very sure that you never ever post the before and after dumps, along with a description of what you did in between, or even take some snapshots as instructed.No sir, all this math buffs and (professional) reverse engineers here willneverbe able to help you or understand this complicated stuff, no sirCheers,DC1MC

author: drussell
author_rank: Super Contributor
timestamp: April 20, 2018, 09:55:10 pm
content: Quote from: ESXi on April 19, 2018, 04:05:41 pmYou could have also just searched for 93C46.Searching for the base part number without prefixes and suffixes is generally the best course of action when searching for things that have many variants and manufacturers.Quote from: DC1MC on April 20, 2018, 09:22:49 pmLOL...Indeed...

author: wmj259
author_rank: Newbie
timestamp: July 03, 2018, 01:24:36 pm
content: Hi,I am having a similar issue with reading from a FairChild 93C56EiM8 chip.I have an arduino and have been changing it up a bit, but am not able to read it successfully.I found two codes, one being the tim0s Microwire and the other beinghttp://ingenieriaencasa.blogspot.com/2017/03/leer-y-escribir-memoria-93cseries.html.I did find a third code (http://forum.pvtech-ecu-research.com/viewtopic.php?t=3) that seemed to give me reasonable results, but am not able to confirm. I did buy a chip programmer from ebay, but it doesnt support Microwire protocol.My issue is that these codes have the ORG pin, but the chip I have doesnt show that.My chip data sheet:https://www.digchip.com/datasheets/parts/datasheet/161/FM93C56EM8-pdf.php.