Possible input frequency range of SN75176B

Taichi Noda

Expert 1350 points

Other Parts Discussed in Thread: SN75176B

Hi,All

Let me ask about an input possible frequency of SN7516B.

How much is max frequency clocks of waves of input?

And,can I calculate an answer from switching characteristics?

Best Regards.

over 11 years ago

0 Ron Michallick over 11 years ago

TI__Guru**** 165666 points

Taichi,

The recommended maximum clock rate is 10Mbps (100nS bit time).
The bit transition time is 30nS max, so at least 70nS of each bit is data.
Good signal quality is expected at this data rate.

0 Taichi Noda over 11 years ago in reply to Ron Michallick

Expert 1350 points

Hi,Ron

Thank you for quick reply.

You helped me a great deal.

I have an additional question.

If you know it ,please let me ask you.

How much percentage is an acceptable error of SN75176B?

Best Regards.

0 Ron Michallick over 11 years ago in reply to Taichi Noda

TI__Guru**** 165666 points

Taichi,

Please explain the question. I am not certain that I understand.

0 Taichi Noda over 11 years ago in reply to Ron Michallick

Expert 1350 points

Hi,Mr.Ron

I'm sorry for my confusing questions.

I meaned , how mush pacentage is an allowance accident error of RS485 baud rate?

As a result of my research,I think that it is differ depending on bit size and method of micro computer .

Best Regards.

0 Ron Michallick over 11 years ago in reply to Taichi Noda

TI__Guru**** 165666 points

Taichi,

The RS485 signal is data only so the transmitter and receiver have separate clocks. Every time the data bit changes the receiver can synchronize its clock. In a 8 bit even parity data stream (worst case), sending a 0x00 will have 10 low bits in a row. At the end of the 10 bits, the receiver clock must still be accurate. With 10Mbps and 70nS of valid bit time, the clock must sample in this window of time. In other words the clock must be better than +/-3.5nS error over 100nS [+/-35nS/(100nS*10)]; This is 3.5% error.

0 Taichi Noda over 11 years ago in reply to Ron Michallick

Expert 1350 points

Hi,Ron

Thank you for quick reply.

I made a diagram that you meaned,but follow diagram is a content you meaned correct?

And,Where are two informations that Max data rate is 10Mbps and data fix time is 70nS written on a datasheet?

Best Regards

Taichi

0 Taichi Noda over 11 years ago in reply to Taichi Noda

Expert 1350 points

Hi,Mr.Ron

Please let me ask you an additional question about handling UART terminal.

My customer said that they make CPU(control board) connect with SN75176B( communication board)by an electrical harness.

In this case,how should they handle UART(Tx,RX) ? Pull-up? Pull - down? no need to fix level?

I'm sorry for my lack experience.

Best Regards.

Taichi.

0 Ron Michallick over 11 years ago in reply to Taichi Noda

TI__Guru**** 165666 points

Taichi,

There are good resources here. http://e2e.ti.com/support/interface/industrial_interface/m/videos__files/default.aspx

Try the RS-485 Design Guide first

Interface

Interface forum

Possible input frequency range of SN75176B