The Function of uPP START Signal in Receive Mode

Tsutomu Furuse

Hi.

I know that there are many threads of this kind of question in E2E. But I could not find any answers which describe the function of the uPP START signal in the receive mode from the threads.

Would you please tell me how uPP handles the START signal in the receive mode?

The C6746 TRM just says "in receive mode, START is an input signal and may be disabled using the STARTx bit in UPICR.".

One of my customers would like to know it to design a connection with FPGA.

Best regards,
Tsutomu Furuse

over 8 years ago

0 Titusrathinaraj Stalin over 8 years ago

TI__Guru** 116100 points

Hi,
How you are going to access the uPP i.e which mode ?
Transmit mode or Receive mode ?

For uPP transmit mode, START signal is mandatory to indicates first data word per line of data.
For uPP receive mode, START signal is optional.
You can check the "Required signals for various modes"

You can check the signal timing diagrams, START signal will active high on first word when the data transmit/receive from/to uPP.

0 Tsutomu Furuse over 8 years ago in reply to Titusrathinaraj Stalin

Expert 1435 points

Titus,

Thank you for your quick reply.

The access is the receive mode.

I'd like to know for which case we should use the START signal and for which case we can disable the START signal.

Best regards,
Tsutomu Furuse

0 Titusrathinaraj Stalin over 8 years ago in reply to Tsutomu Furuse

TI__Guru** 116100 points

Hi,
Please refer to the following TI E2E posts.
e2e.ti.com/.../422173
e2e.ti.com/.../1322240
e2e.ti.com/.../124882

0 Tsutomu Furuse over 8 years ago in reply to Titusrathinaraj Stalin

Expert 1435 points

Titus,

Thank you for the introduction of the posts.

So, in the receive mode, we don't need the START signal at all?

And we should always disable it with the STARTx bit in UPICR for the receive mode use case?

Best regards,
Tsutomu Furuse

0 Bill Taboada over 8 years ago in reply to Tsutomu Furuse

TI__Mastermind 42545 points

Hi Tsutomu,

The START signal is not required by the receive path. If the START is enabled, it will be used to mark the data that is loaded into the first position in a line. If the START is not enabled, the first data with a valid clock and enable present will be loaded into the first position in the line. The line will continue to be filled until the byte count has been reached.

If you do not need to align the data entering the uPP to a particular byte then you can disable the START signal.

If you need to identify the first channel for some purpose, you will need to enable the START signal and generate the signal for the first word of the line transfer.

Regards,

Bill

0 Tsutomu Furuse over 8 years ago in reply to Bill Taboada

Expert 1435 points

Bill,

Thank you very much!
Now I understand that the START signal is functional to find the first byte in the data bus.

Best regards,
Tsutomu Furuse

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The Function of uPP START Signal in Receive Mode