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PCM2704C: Not clocking CK for the EEPROM

Harald Hellmann
Prodigy 80 points
Part Number: PCM2704C


I'm working with the PCM2704C for a bus powered interface which is already working. Now I want to use the EEPROM to modify the product string. The PSEL and HOST pin is connected to VDD. The D+ pullup can be connected after EEPROM reading is done. DT to SDA has a pullup. So I'm sure that I have everything done what has to be done. Also a college has checked your requests against the schematic. My problem is the PCM2704C doesn't starts clocking at CK for reading the EEPROM. What else can I check? Could there be any reason why no clocks appear?

Why is within the datasheet SBFS036B PCM2704C … in figure 35 the EEPROM connection CK to SCL and DT to SDA but within figure 36 the connections are crossed. Which means DT is connected to SCL with a pullup and CK is connected to SDA. This should be wrong. Within SLEU114 PCM270xEVM-U in figure 2 it is crossed also but now with a pullup at the CK to SDA connection. That is not the quality which I know since 50 years.

  • 0
    TI__Mastermind 49160 points

    Hi Harald,

    I don't have an EVM immediately on hand to test this, but I'm having one shipped quickly. I can also use it to take a look into the incorrect schematics on the EVM. Sorry that they appear to be wrong. Thank you for bringing it up.

    As for the CK output can you share the schematic with me? Also do you see CK being pulled high or is it all low?

    Thanks,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 80 points

    Dear Jeff,

    I'm sorry but we have a clock. I'm running a level translator between the PCM2704C and my µC. The level translator was disabled by mistake and I was measuring on the µC side where I had no clock at all. But I have figured out a couple of other problems with the PCM2704C. The PCM2704C starts clocking about 500µs after power on where my µC didn't has booted. Which I solved. Next we have a dynamic product string but the PCM2704C doesn't accept clock stretching if the next transmission byte isn't prepared fast enough. I have solved this by exclusively running for I²C and not doing anything else  as well as preparing the byte before it is read. Therefore you can close this case but it would be very helpful for others is this information would be given within the data sheet. Thank you.