Key Fob IC identification help

[gkmaia]

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.

[amyk]

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

[gkmaia]

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?

[gkmaia]

schematic updates

[fzabkar]

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

Page 10 talks about the EEPROM content at delivery.

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.

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").

[ijchan223]

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