TL16C550D: Data buss state at Reset condition

Hey Muk,

Yusuke Mukuno said:

Part Number: TL16C550D

Hi Expert,

My customer have some questions about TL16C550D,

Question1,

Could you please let me know the data buss state at Reset condition?

(e.g, High-Z?)

[Bobby] You mean when you hold the device in reset (reset held HIGH and NOT toggled)?

Question2,

If TL16C550D resisters  will be accessed at reset condition, What value would the device return?

(e.g. In case of Data buss is high-Z, it is depend on external pullup.)

[Bobby] The parallel interface (D0-D7) and serial interface (Tx) are push pull so you should not require pull up resistors on the bus. Are you asking about series resistors in the case where the lines are NOT HI-Z when reset is held HIGH?

Thanks

Muk

Please see my comments above.

-Bobby

HI Bobby-san,

Thank you for your reply.

For Question1, Yes it is meaning when  MR pin is held high.

For Question2, sorry for your confusion. customer question is

If TL16C550D will be accessed any communication from other device when the MR pin is held HIGH, How will the state of parallel interface (D0-D7) and serial interface (Tx) look from other device?

Thanks

Muk

Hi Bobby-san, thank you for your reply

I'm sorry to say that TL16C550DPT datasheet shows

[Data bus. Eight data lines with 3-state outputs provide a bidirectional path for data, control, D4 47 and status information between the ACE and the CPU.]

and SC16C550B (NXP) datasheet shows

[Data bus. Eight data lines with 3-state outputs provide a
bidirectional path for data, control and status information
between the UART and the CPU.]

Please make sure which is correct answer, push/pull or 3-state outpus.

And I'd like to know the behavior during resetting.

Best regard,

Tomo

Hey Tomo,

Apologies I've been out of the office.

I believe the parallel lines are supposed to be HI-Z (3-state as you put it) when the device is held in reset however to try to confirm this, I've reached out to someone in our design team to see if they can double check this. I'll see if I can get an answer from him by tomorrow.

-Bobby

The design engineers got back to me today. It looks like they can't help verify this in a design sim so this means I will need to place an order for a breakout board and samples of the device to verify for you. I should have an idea of when I can test this in the lab by next week.

-Bobby

Bobby-san

Do you have any update?

Thanks

Muk

Muk,

I've place an order for sample devices and a breakout board to test them. I am still waiting to receive them.

-Bobby

Bobby-san,

Do you have any update? Can you get the test board?

Muk

Hey Muk,

I went into the office Thursday to see if the breakout board came, turns out it wasn't delivered. I pinged our Admin who placed the order to contact the supplier and heard back that they were delayed in shipping it so it ended up shipping on Friday instead. I've received the breakout today (need to double check if its correct) and will see if I can submit a soldering request to a lab tech, after that is finished I should be able to verify for you. I expect I should be able to have results by end of day Friday at the latest (and earliest is tomorrow if the soldering request is finished in time).

-Bobby

Muk,

I've got the boards back from the solder technicians. I'll see if I can make the measurements for you this weekend since this has been in the queue for quite a while.

Sorry for the delay,

-Bobby

Hi,  Bobby and Muk,

Thank you for your help.

I could solve the problem.

Take care, Tomo