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Electronics => Repair => Topic started by: gkmaia on November 12, 2020, 07:31:55 am

Title: Key Fob IC identification help
Post by: gkmaia on November 12, 2020, 07:31:55 am

I got a key fob that is faulty.

From what I can see the there is a crystal and a Philips RF ID transmitter.

From what I could find it has an SSOP20 eprom in it so I suspect that is where they store the programming and the code. The other IC is a SSOP16 and not sure that is for. Seems to be driving the crystal from pins 10 and 11.

Then it gets myself confused as I from what I could learn the driving transmitter IC is usually connected to the the crystal and the other IC is where they store the code.

Anyone with some experience on these things? My goal is basically to replace the transmitter hopping the other ic holds the code.

Title: Re: Key Fob IC identification help
Post by: amyk on November 13, 2020, 01:31:28 am

One is a PCF7321 (seems equivalent to PCF7921), the other one I can't read the markings on.

Title: Re: Porsche Key Fob IC identification help
Post by: gkmaia on November 14, 2020, 05:35:15 am

Seems to be but the pinoput does not match

I did a schematics of the PCB. I think the other IC is a Tda5001 frequency synthesizer.

So bsed on that the ID code is defintevilly on the philips right?

Title: Re: Key Fob IC identification help
Post by: gkmaia on November 14, 2020, 11:52:05 am

schematic updates

Title: Re: Key Fob IC identification help
Post by: fzabkar on November 16, 2020, 11:17:21 am

Here is the datasheet for the PCF7x41 single-chip solution:

PCF7x41ATJ, NXP, Security Transponder and RISC Controller (STARC 2XLite):
https://media.digikey.com/pdf/Data%20Sheets/NXP%20PDFs/PCF7x41ATJ.pdf (https://media.digikey.com/pdf/Data%20Sheets/NXP%20PDFs/PCF7x41ATJ.pdf)

Page 10 talks about the EEPROM content at delivery.

Quote

Bit 7 to 4 of this page (Identifier) serve the function of a product type (application) identifier and are set to ‘0110’ for the PCF7x41ATJ. For system compatibility reasons, the same product type Identifier is used by PCF7x21 (KEECOR).

AISI, the PCF7x21 chips are the predecessors of the PCF7x41 and are part of a 2-chip solution.

Page 4 of the same datasheet explains the part number coding.

Quote

PCF7941ATJ/CA1B00E0 represents the E-ROM product for development and applications with low quantities.

PCF7941ATJ/CA1Brrff represents a customized E-ROM product.

PCF7341ATJ/C0ABrrff represents the ROM coded product for high volume applications.

So the "73" chips are ROM versions while "79" chips are E-ROM versions ("FLASH like features").

Title: Re: Key Fob IC identification help
Post by: ijchan223 on November 22, 2020, 04:56:00 am

what does it go to, a fob from early 2000s should be easily programmed with a sequence and the key.