ST 72104 - Port B inputs w/pull-up but without interrupt

[lhaas]

Posted on May 08, 2003 at 08:40

ST 72104 - Port B inputs w/pull-up but without interrupt

[lhaas]

Posted on May 07, 2003 at 11:26

I'm using ST 72104G1.

How to configure Port B with some pins as input with pull-up WITH interrupt and some others pins as input _with pull-up_ WITHOUT interrupt ?

TIA

[rolf]

Posted on May 08, 2003 at 06:21

This controller does not offer the possibility to configure the internal pull-up resistor without interrupt. So in this case you have to choose ''floating input'' with an external pull-up resistor.

Take care if you use more than one pin on port B as interrupt input: all interrupt pins are connected trough an NAND-gate to the sensivity control block of the interrupt logic. So only an edge change on the output of the NAND will trigger an interrupt. You should think about all possible state changes on the input of the NAND if more than one pin is connected to it: You will see that in some cases the second interrupt pin will not trigger a new interrupt if the first one has a certain state depending on the interrupt sensitivity you have configured!

If you have to deal with two external interrupt signals I recommend to put one on interrupt source ie0 and the other one on interrupt source ie1. If you have more than two signals you should think about to use also the input capture pins of the 16-bit timer to make your life easier!

Ciao, Rolf

[lhaas]

Posted on May 08, 2003 at 08:40

Hi Rolf and thanks for ur reply

Then, i'll use floating inputs and pull up resistors. And Ok for NANDed interrupts. I'll consider that also.

Best regards

Laurent (aka Efcis)