I am trying to create an output unit for 8086 microprocessor which is connected to MP's 00ABh(10101011) address. I used 74LS373 for that. This is how I made connections:

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When I run the code below, LED's shows the address value (00ABh) instead data value (18h).

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What am I doing wrong here?

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    \$\begingroup\$ If I can read that schematic, you're latching data into U3 on a signal called Address Latch Enable. What do you expect to happen? \$\endgroup\$ – Brian Drummond Oct 3 '17 at 20:23
  • \$\begingroup\$ Where is the address bus coming from? I do not see a driving source of any kind in the included schematic \$\endgroup\$ – DerStrom8 Oct 3 '17 at 20:30
  • \$\begingroup\$ @DerStrom8 I can not upload more than 2 image because of the reputation thing so i could not show that part. I need to locate an output unit to 00ABh address. With 74373, I am trying to give an output if the given address is 00ABh so i put a decoder there for that. And it should be a read operation from IO thats why I added these parts to decoder. Then I used logic 1 for ALE entry. What is wrong here? \$\endgroup\$ – Erkan Oct 3 '17 at 20:46

You are using the wrong control signal ALE which latches the address part and I have no idea why you are enabled the output with the decoded signal.

I'd also switch to a 374 edge triggered device clocked by that decoded signal.

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  • \$\begingroup\$ I need to locate an output unit to 00ABh adress. That's why I used that decoder part. ALE is logic 1 when there is address information on address/data bus. Is it wrong? How can i make LEDs to show data value(18h) instead address value(00ABh, LEDs shows address value now)? \$\endgroup\$ – Erkan Oct 3 '17 at 20:42
  • \$\begingroup\$ ALE goes high when the address is presented... not the data. And even then.. the address is only guaranteed valid on the falling edge of ALE. \$\endgroup\$ – Trevor_G Oct 3 '17 at 20:43
  • \$\begingroup\$ Sorry sir. I got it but I am little bit confused. So how can I make that LEDs to show data value? \$\endgroup\$ – Erkan Oct 3 '17 at 20:51
  • \$\begingroup\$ YOu need to latch the address (or the decoded address) on falling edge of ALE and then use that to enable a clock to a 374 with the WR/ line \$\endgroup\$ – Trevor_G Oct 3 '17 at 20:55

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