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).