


>>>>>>>>  TEST5082


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TARGET
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This is code to go into ROM U33 on an IBM 5150 (IBM PC) motherboard.
The IBM 5150 has special ROM requirements. See http://www.minuszerodegrees.net/5150/motherboard/5150_u33.htm


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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 the BIN file into a suitable ROM/EPROM/EEPROM.
   The IBM 5150 has special ROM requirements. See http://www.minuszerodegrees.net/5150/motherboard/5150_u33.htm


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BIN FILES
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Per http://www.minuszerodegrees.net/5150/motherboard/5150_u33.htm, if a suitable adapter is used, 16 KB and 32 KB sized ROM/EPROM's can be used on the IBM 5150 motherboard.
Because of that, included here are 16 KB and 32 KB versions of TEST5082_8KB_SIZED.BIN, being TEST5082_16KB_SIZED.BIN and TEST5082_32KB_SIZED.BIN

TEST5082_8KB_SIZED.BIN is for an MCM68766 EPROM, or a 2564 EPROM.
TEST5082_16KB_SIZED.BIN is for a 27C128 EPROM (in a suitable adapter).
TEST5082_32KB_SIZED.BIN is for a 27C256 EPROM (in a suitable adapter) or W27E257 EEPROM (in a suitable adapter).

Again, see http://www.minuszerodegrees.net/5150/motherboard/5150_u33.htm


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WHAT DOES THE CODE DO ?
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About every two seconds, the PB2 pin (pin 20) of the motherboard's 8255 chip is toggled between logic HIGH/LOW states.
The toggling never stops.
The toggling can be observed by monitoring the PB2 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 20 of the 8255 chip being HIGH, then about two seconds later change to logic LOW, then about two seconds later change to logic 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 20 of the <a href="8255.png">8255</a>.

The 'TEST5082_video_multimeter.mp4' video shows what is seen if a multimeter (in 'DC voltage' mode) is used.









