


>>>>>>>>  TEST5083


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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 TEST5083_8KB_SIZED.BIN, being TEST5083_16KB_SIZED.BIN and TEST5083_32KB_SIZED.BIN

TEST5083_8KB_SIZED.BIN is for an MCM68766 EPROM, or a 2564 EPROM.
TEST5083_16KB_SIZED.BIN is for a 27C128 EPROM (in a suitable adapter).
TEST5083_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 PB3 pin (pin 21) 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 PB3 pin via a logic probe, or via a multimeter (in 'DC voltage' mode).
Because the PB3 pin activates/deactivates the motherboard's relay, you can also observe the toggling via the relay.


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WHAT YOU SHOULD OBSERVE
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1. Expect to see (and hear) the relay changing state every two seconds.
   The 'TEST5083_video_relay.mp4' video shows that.


2. Expect to see pin 21 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) to do that:
   - 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 'TEST5083_video_multimeter.mp4' video shows what is seen if a multimeter is used.











