What about expand the inputs via a I2C device?

What about this:
http://www.semiconductors.philips.com/acrobat/datasheets/PCF8575_3.pdf
(16-bit) it can make a interrupt for you also when a key is pressed =
(change
of state on input pin)!

Or: =
http://www.semiconductors.philips.com/acrobat/datasheets/PCF8574_2.pdf
(8-bit)

Best regards

Ole Andreas Gl=F8ersen
LA9SHA




-----Opprinnelig melding-----
Fra: Bala Chandar [mailto:Bala.Chandar@AVENTIS.COM]
Sendt: 10. desember 2001 12:12
Til: PICLIST@MITVMA.MIT.EDU
Emne: Re: [EE]: Which is the ideal IC?


In my circuit, I am using all the 8 pins of Port B and pin 6 of Port A =
as
inputs to detect the closing of 9 PB switches. The PIC used is 16F628 =
with
internal RC Oscillator. Port B weak pull-up is enabled and PortA.6 has =
a
4.7K pull-up resistor.

As I am running short of I/O pins, I want to use an IC to reduce the =
number
of pins used by the PIC for detecting key pressings. After a  search =
through
CMOS data book, I found 74HC147 (10 to 4 Priority Encoder) almost ideal =
for
the purpose. With this IC, I will need only 4 pins of the PIC and as =
many as
5 pins will become available.

Now, my question: Is there a better IC for the purpose?
Please let me know if there is.

Thanks & Regards,
Bala

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