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1 year ago

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IO open drain configuration question.

Hi,

I read in the Cyclone IV device handbook that I/O pins can be configured in open-drain mode.

However, I couldn't find the chapter that explains how to set this up.

I tried using the Pin Planner in Quartus IDE, but I couldn't find an option to configure open-drain mode there.

Could you guide me to an example or instructions for setting this up?

Thank you!

Adam Shiau

FvM
1 year ago
Hi,
you don't need assignment pin planner or assignment editor to implement open drain, you can also infer open drain output directly in HDL by driving an inout pin to '0' and 'Z' respectively. Resource Property Editor shows that open drain mode is implemented for output buffer.

SDA <= '0' WHEN sda_oen = '0' else 'Z';

Default compiler setting AUTO_OPEN_DRAIN_PINS on is presumed.
Regards
Frank

3 Replies

AqidAyman_Altera
Regular Contributor
1 year ago
Hello Adam,

Have you been able to look at the Assignment Editor?
You open the Assignment Editor by clicking Assignments > Assignment Editor.
The Assignment Editor allows you to view, create, and edit assignments.
FvM
Super Contributor
1 year ago
Hi,
you don't need assignment pin planner or assignment editor to implement open drain, you can also infer open drain output directly in HDL by driving an inout pin to '0' and 'Z' respectively. Resource Property Editor shows that open drain mode is implemented for output buffer.

SDA <= '0' WHEN sda_oen = '0' else 'Z';

Default compiler setting AUTO_OPEN_DRAIN_PINS on is presumed.
Regards
Frank
AqidAyman_Altera
Regular Contributor
1 year ago
Thank you, Frank, for your valuable input.

Hi Adam,

I wish to follow up, do you need more support on this matter?

Regards,
Aqid