PPI 8255 w parallel port 0x378

hi, this is my schematic :

**broken link removed**

#include <conio.h>
#include <stdlib.h>
#include <stdio.h>
#include <dos.h>

void main()
{
do
{
outportb(0x378, 0x80); <--- (0x80 ) set all PPI ports to output mode (10000000)
delay(900);
outportb(0x37a, 0x00); <--- makes the PPI read address A0 and A1 read with 0x80 data,
delay(900); <--- C0 and C1 at parallel port 0x37a are inverted, means 0 are 1, and 1 are 0
outportb(0x37a, 0x03);
delay(900);
outportb(0x378,0x00); <--- output to portA with data 00
delay(900);
outportb(0x378,0x01); <--- output to portA with data 01
delay(900);
outportb(0x378,0x02);
delay(900);
outportb(0x378,0x04);
delay(900);
}
while (!kbhit());
}

why it isnt working..?

but what i have look with 'port analysis' , output from parallel port does working... its running..
but it wont "get in" to 8255 chip..
and also i use "giveio" program to open ports with winXp

**broken link removed**


and how high does voltage from data bus D0-D7 output from parallel port ? is it 5v ?
because my computer only gives less than 2 volt..
is that enoungh to work with 8255 ?

HI,
You have connected /WR to logic 0 permenantely,
So the 8255 is always in write mode
but when you write something to 8255 and to transfer that data to the actual pin, the /WR has to go high and after some delay the data appears on the port pins

https://www.electro-tech-online.com/custompdfs/2005/05/fn2969.pdf
refer to waveforms on page 7 in the above link

WR to HIGH ?

isnt if i want to send data from D0-D7 paralel port to control word PPI8255 it require LOW for WR ?
and from parelel port to port A PPI8255 also require LOW for WR ?

or i just doin wrong.. :lol:

Have you properly reset the 8255 when it is first powered ON before sending commands to set its operating mode?

Check the below figure
When /WR is low the data is written to port A register
and when /WR becomes high the data in port A regsiter appears at output which is the physical pin

Is all you want to do drive 4 LED's from your parallel port?, if so, why are you messing about with an 8255?.

ctrl-alt ,
notice that on the rising edge of your Write signal is when the data is available..
now i am not positive on this , but , you may still have to latch the data ,to be able to see it..