


>>>>>>>>  TEST6083


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TARGET
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This is 32 KB sized code to go into ROM U18 (which is 32 KB sized) on an IBM 5160 (IBM XT) motherboard.

If your IBM 5160 motherboard is a 64-256KB type, the TMM23256/MK37000/MK38000 ROM's can in most cases be replaced with 27C256 EPROM's,
but some brands of 27C256 may be unsuitable for the 64-256KB motherboard - see http://www.minuszerodegrees.net/5160/motherboard/5160_u18_u19_sockets.htm
     
If your IBM 5160 motherboard is a 256-640KB type, then you can use a 27C256 (or 27256) EPROM, or a Winbond W27E257.
      
For the IBM 5160, use EPROM's that are rated at 250 ns, or faster.
See http://www.minuszerodegrees.net/5160/motherboard/IBM%205160%20motherboard%20-%20ROM%20description%20from%20TR.png


The code also suits XT clones that have a single 32 KB sized BIOS ROM (e.g. 27256 or 27C256).


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REQUIRED
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1. Either a logic probe, or a multimeter (and the knowledge of how to use it to measure DC voltage).

2. A way of putting TEST6083.BIN into a suitable ROM/EPROM/EEPROM.


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WHAT DOES THE CODE DO ?
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About every two seconds, the PB3 pin (pin 21) of the motherboard's 8255 chip is toggled between HIGH/LOW.
The toggling never stops.
The toggling can be observed by monitoring the PB3 pin via a logic probe, or via a multimeter (in 'DC voltage' mode).


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WHAT YOU SHOULD OBSERVE
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Expect to see pin 21 of the 8255 chip being HIGH, then about two seconds later change to LOW, then about two seconds later change to HIGH, etc. etc.

If using a multimeter (instead of a logic probe):
- Put meter into 'DC voltage' mode.
- Put the negative probe on pin 7 of the <a href="8255.png">8255</a> (or on any ground).
- Put the positive probe on pin 21 of the <a href="8255.png">8255</a>.

The 'TEST6083_video_multimeter.mp4' video shows what is seen if a multimeter (in 'DC voltage' mode) is used.

