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TL16C552: 8MHz UART also runs at 16MHz

James Elliott1
Intellectual 1260 points
Part Number: TL16C552

Hi Team,

A customer is looking at both the TL16C552 and the TL16C552A.

They have installed the TL16C552FNR in one of there designs and according to the data sheet, the TL16C552FNR has a max. Ext. Clock of 8 MHz.

In this instance there product has a 16 MHz external clock. Nevertheless, the TI UART runs with this double clock.
Can you help explain why?

The customer has  now switched to TL16C552AFNR UART, as this has an ext. clock of 16MHz. However, the customer would like to know why the mentioned UART 8MHz also runs at 16MHz.

Could you share your thoughts and any information you have?

Regards

  • 0
    TI__Genius 15345 points

    Hi James,

    I'm a little bit confused by what the customer is asking. When they say TI UART what are they referring to? Are they asking, why can the A version of the device handle double the external clock speed?

    Best,

    Chris

  • 0
    TI__Intellectual 1260 points

    Chris,

    The customer has been able to share a bit more context and correct his initial query.

    There basic problem is that In the past they used a UART from EXAR.
    Type: ST16C552CJ68-F. This device is now EOL.

    They intern then selected and used our UART -  TL16C552AFNR

    The question they have is:


    "Are these UARTs TI and EXAR compatible or are there differences that must be taken into account???

    In principle, the Texas UART works in small system configurations. But the more modules are used (programmed) in our system expansion, the result is that the Texas UART no longer works.
    (8-bit data bus and 3-bit address bus here) in parallel.

    Note:
    The Texas UART was originally and accidentally (typo)
    with type: TL16C552 FNR (8MHz Clock) used.
    Hence my original request."

  • 0 in reply to James Elliott1
    TI__Genius 15345 points

    Hi James,

    Is the customer looking to see if these two devices are drop-in compatible? I can already tell they are not. There are some differences in the electrical characteristics at the very least. 

    James Elliott1 said:
    In principle, the Texas UART works in small system configurations.

    Does this mean that the customer tested their system with 1 or 2 devices and it worked? If this is the case then we can look to debug the issue when multiple devices are added. 

    Has the customer shared any specifics as to what stops working with this UART device when they add more modules to the system? How many UART devices are in their system?

    Once I get this information we can go from there and start to debug the issue.

    Best,

    Chris