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TL16C752D: Not asserting LSR[5]

Part Number: TL16C752D

Hello,

LSR[5] is not often asserted after transmitting interrupt with 9600bps rate in spite of IIR = 0xC2(THR interrupt).

LSR[5] is asserted in the following condition.

  - 4800bps rate or waiting 500ns after interrupt or using the TL16C752B device

What is this not asserting caused by?

Can the TL16C752D assert LSR[5] with 9600bps?

Best Regards,

Kuramochi

  • Hey Kuramochi,

    The 752D should be able to assert LSR[5] at any of the baud rates.

    "- 4800bps rate or waiting 500ns after interrupt"

    It sounds like if you are able to see the LSR update bit 5 (after 500 ns), the timing for the LSR register to update seems to correlate to the interrupt asserting first. (I would need to do testing to confirm if this is true). Based on this, can the customer wait the 500ns before reading the LSR register or base their code to rely on the interrupt instead of the LSR?

    "or using the TL16C752B device"

    I recall a design engineer stating the timing between the B and D version of the device differs. When the C version was made from the 752, the difference between B to C had to do with a change from being synchronous to asynchronous in relation to the input clock. D version likely borrowed some of the IP from the C version and this may be why there is a difference in registers being updated between the B and D versions of the devices.

    -Bobby