ISA Bus

[ZainZeus]

So Here I Go!
I'm not a native english speaker so don't get mad of me

I'm performing a project for an ISA data adquisition card, so I investigated a little about the ISA bus and the PPI 8255 wich is a periperial programmable interphase, but what I need is to see the signals of the IOR, IOW, ALE, AEN and the adresses outputs in the ISA groove, so I connect them to some 74ls244 buses so I can see the signals on some leds. BUT, I don't see what I'm supposed to see when I program a simple outport() command in the turbo C++ 3.0, instead only noise is what I see. Maybe I'm wrong on what I must see? or What must I see?
I hope there's someone who has worked on ISA bus.

 

[Thrashbarg]

There are a lot of other processes on a computer when a program runs. Interrupts are a good example. This is probably the noise you are seeing.

I have an excellent book on this subject, 'Interfacing to the IBM Personal Computer', 1983, Lewis C. Eggebrecht. Maybe you can find it at a library?

 

[mbbrutman]

I second the recommendation on that book - it has all of the signals and timing information you need.

Can you describe your method with the LEDs and the 74ls244s? Are you latching addresses and data? If not, you are in trouble .. the signals are fairly fast unless you have a logic analyzer.

 

[ZainZeus]

Well thanks for answer mbbrutman,
I made a schematic on orcad (I hope you got it) the idea is to put the control signals (I mean the ALE and the AEN ) for security reasons in to a 244 and then put the AEN as the LE on the latch 74HC373 so as I can hold that signals until the next ones. but they aren't holded, but the worst is that when run the program wich I made, sometimes I don't see a thing.

I include the program I'm usin

#include <stdio.h>
#include <dos.h>
#include <conio.h>
#define p_data 0x300



int main(void)
{
int value = 2;
int i;

while(!kbhit())
{
clrscr();
for(i=0;i<4;i++)
outport(p_data, value);
printf("Value %d sent to port number %d\n", value, p_datos);
delay(50);
}
getch();
return 0;
}


Greetings