unused pins in ADUC842/ADUC843

what i meant was should i use a pull up/pulldown
or should i keep it as floating?

what i meant was should i use a pull up/pulldown
or should i keep it as floating?

what i meant was should i use a pull up/pulldown

Well now. It all depends upon which pins you want to leave disconnected.

It is quite normal for the datasheet of the device to tell you what to do with them.

What does it tell you?

"Port 3 is a bidirectional port with internal pull-up resistors. Port 3 pins that have 1s written to them are pulled high
by the internal pull-up resistors, and in that state can be used as inputs. As inputs, Port 3 pins being pulled
externally low source current because of the internal pull-up resistors."

This is what it is telling...

As per my understanding it means that since internal pull up is there so we can leave the pin as floating if we dont want to use the pin

Am i right?

As per my understanding it means that since internal pull up is there so we can leave the pin as floating if we dont want to use the pin
yes, if you are not planniong for your device to work in a noisy environment.

Erik

There are EMI/EMC issues.

so I cant leave them floating.

The option I have is to pullup or pulldown the pins by a resistor

What should I do den?

Regards,
Mayuri

so I cant leave them floating.
if mains powered, write a '0' to them and they will be 'shorted' to ground
if you absolutotally have to do something externally, verify that your derivative does the standard 'reset state' of the pins, stay away from those pins in your code and tie them directly to Vcc.
if you are 'afraid' of the above tie them through a resistor to Vcc.

anyhow, what does this have to do with Keil siftware, for '51 hardware 8052.com is the place

Erik

I do not know the ADUC and thus
if mains powered, write a '0' to them and they will be 'shorted' to ground and, if your derivative has configurable ports, configure them as input/open drain/quasi bi-directional.

if you absolutotally have to do something externally, verify that your derivative does the standard 'reset state' of the pins quasi bi-directional and '1', stay away from those pins in your code and tie them directly to Vcc.

if you are 'afraid' of the above and the conditions are as above tie them through a resistor to Vcc.

Erik