Raghunathan R wrote:
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Since you want to read three channels, you have to get control over the address,ALE,EOC, and SC pins.

this is what i,m asking about, how to control it with 555 timer.
as i understand, you might thinking that i wanna to connect 555 timer to the emulator board. NO i,m going to use separate circuit for that also a separate circuit for ADC.

the 8255 in my board is connected to the address bus, i dont think so i,m able to set or reset that P0!! i,m i right.

this is the board that i,m cunrrently using

http://chaokhun.kmitl.ac.th/~kswichit...bblock.gif



Raghunathan R wrote:
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*If all is well you should not see anything other than a "00" or an occassional "01". If you see any other value that keeps rolling, jumping etc then the setup is not optimal. And mostly the problem is with the ground.

i think you mean that jumping through the program???

what i,m thinking is that, i would like to use just like this circuit.
http://www.electronic-circuits-diagrams.com/computers...ages/2.gif

Regards
Albarkani