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82c55

When the PIA is inserted in the board ..current  consumption is ~ 280-300mA  .

To test the chip operation .. look up specks on 8255 .. There should be tons on the internet ...  Intel 8255

In this case we can test the port A of the PIA via PipBug.

Port addresses are:
  • Control register=7003H,
  • Port A =7000H

So what is needed is to set port A to output say ....  and all other ports to input...

From 8255 data... that would make the byte to control register (7003H) equal to  --> #8B  (hex)  ... and if we send ... say ... #F0 to address 7000H .. that would turn top 4 bits on and other 4 low bits off on port A.

PipBug Commands (red is user input)

Modify control register..
*A7003<cr>
7003 XX 8B<cr>

Modify Port A ...
*A7000<cr>
7000 XX F0
<cr>

At this point you should be able to examine the Port A pins ... and check that half of port pins are high and half are low ... (logic probe is a good test unit .. or a voltmeter of some sort).