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PGA460: how much is the maximum Inter-Field Wait Time PGA460 allowed in UART mode, can I split a long UART CMD into several portion

AaronD
Prodigy 130 points
Part Number: PGA460

Hi,

how much is the maximum Inter-Field Wait Time PGA460 allowed in UART mode?

the datasheet says "Inter-field Wait Time (1 bit period)", is that means 1 bit maximum ?

there is some concerns regarding the UART interrupt priority and how frequently MCU should server the UART for PGA460. 

after all the PGA "Transducer echo data dump" CMD has 128 bytes, I am trying to find the feasibility to break this 128 bytes long transmit into several portion, add a few bit interval in between the transmit portion. then MCU has more time to serve other tasks.

Thanks,

Aaron

  • 0
    TI__Mastermind 27780 points
    Hi Aaron,
    Yes, the Inter-field wait time must be the equivalent to 1-bit length based on your UART baud rate (t_BIT_UART).

    If you prefer to read back the 128 bytes of echo data dump in portions rather than an entire frame, you can read the echo data dump byte-per-byte using a register read command (PGA460 UART Command9) of the register addresses in the range of 0x80-0xFF. This range is where the echo data dump values are directly accessible.

    With this, you can start with a bulk echo data dump read command (Command7), and if you know when in the bulk read the MCU is interrupted, you can perform a single address read of the remaining echo data dump addresses. Alternatively, you can perform a single address read of the entire echo data dump memory space to avoid having to monitor and track when the bulk read was disrupted.
  • 0 in reply to Akeem Whitehead
    Prodigy 130 points

    Hi Akeem,

    Thanks for your support.

    CMD 9 Register read should work, but there are still CPU load concern as single byte read is less efficient than bulk reading. 

    Do you have a work around to read 16 bytes and wait for 1~5 bytes?

    Thanks

    Aaron

  • 0 in reply to Akeem Whitehead
    Prodigy 130 points

    Hi Akeem,

    I have opposite question regarding long frame below from MCU to PGA460.

    12 EEPROM bulk write(5)

    16 Threshold bulk write(5)

    Does PGA460 work if MCU Tx 8 bytes and a few byte time during CMD 12 and 16? if not work, what will happen to PGA460?

    Thanks a lot,

    Aaron

  • 0 in reply to AaronD
    TI__Mastermind 27780 points
    Hi Aaron,

    Unfortunately, it is not possible to UART read 16 bytes, and wait for 1~5 bytes. You must either use the bulk read or single register read command.

    The PGA460 has not been tested for inter byte delay within a given UART transmit command. This intermittent command read/write support may be more likely supported by the USART (SPI-like) mode given the data out is dependent on the master generated SPI clock.

    The only problem is that there’s an idle timeout counter which checks to see if RXD has been the same value for more than 15ms. If this timer times out, the USART controller is cleared and the transmission ends for a direct data out command.
  • 0 in reply to Akeem Whitehead
    Prodigy 130 points

    Thank you Akeem.

    that address my concern.