Rules of precedence for digital-out driving instruments?

[Guest]

Hi,

 

The Analog and Digital Discovery devices have multiple instruments that can drive the digital outputs:

• DigitalIO
• DigitalOut
• UART, SPI, I2C, CAN protocols

What happens if multiple instruments are active simultaneously? Do some instruments have precedence over others?

Best, Sidney

 

 

[attila]

Hi @reddish

Exactly.

In "pseudo hdl" looks like this:

DIO <= Digital-Out when Digital-IO-OutputEnable = 0 and Digital-IO-Output = 0 else Digital-IO

[attila]

Hi @reddish

The digital IO signals are shared in the device between Digital-IO, Out and In functions. The Digital-IO has priority over Digital-Out. The Digital-Out is only applied for a signal when the Digital-IO Enable and Output are zero for the respective bit.

The protocols use the Digital-In/Out device resources to create various communication protocols. Only one of the protocols can be used at a time. The Digital-Out is used to generate the output signals and the Digital-In to capture the received data. Overriding a signal used by the protocol with Digital-IO may mess up the communication.
Note:
The I2C with clock stretching uses additional signals.
The DIO channe indexing for Digital Discovery starts from 0, 0 is DIO-24, 1 is DIO-25…

[Guest]

Hi Atilla,

Thanks for the clarification.

Just to clear up one final thing about the relation between DigitalIO and DigitalOut device:

If the DigitaIO "OutputEnable" is 0,  and the DigitalIO "Output" is 1, what is then the state of the respective pin? Is it HighZ (irrespective of DigitalOut)?