A microprocessor communicates with peripheral boards via a serial link. Each peripheral board has a unique binary address set by the dip switches on the board. The microprocessor's configuration dictates how many peripheral boards the microprocessor communicates with. When a microprocessor powers up, it performs a self-check and communicates with its peripheral boards in a specific order. If the microprocessor cannot communicate with a board, the microprocessor displays an error message indicating that the board has failed (MKI processors must be configured for peripheral failure).

If a peripheral board fails under a condition that continuously puts noise on the serial link, the peripheral board will "tie up" the serial link. When the serial link is "tied up" no communication can take place. The "tied up" condition caused by the noise on the link causes an error message for the first peripheral board that it attempts to communicate with. SEE ALSO: ELECTRICAL INFOBOARD COMMUNICATION.

BEFORE TROUBLESHOOTING:
----------------------------------------------
- TROUBLESHOOTING THIS PROBLEM REQUIRES STRONG FAMILIARITY AND COMPETENCE IN WORKING WITH ELECTRICITY AND ELECTRONICS.
- Electronic boards in MILNOR equipment are not always located in only one electrical box.
- MILNOR electronic boards are electrostatic sensitive. Ground yourself before handling electronic boards. Handle the boards by the edges; do not touch any components or electrical contact points. Never set the boards down on a conductive surface.
- Always turn the power off when plugging and unplugging electronic boards. Take caution not to ground a live wire and create a short.

TROUBLESHOOTING:
---------------------------------
1. Always determine what was last done to the machine. This will help determine the possible causes of the problem.
2. Check each plug on ALL electronic boards in the machine. Verify that they are plugged into the correct pins. If the plugs on the boards are not properly plugged (i.e. one pin off or not fully seated), the electronic board will not function properly.
3. Check the voltage going to the peripheral boards and the processor board. If the voltages are incorrect, the board will not communicate. Use the schematics for the machine to determine the location and correct values for the voltages.
4. Ohm all serial link wires for continuity. Voltage should be off when ohming the wires. Check the serial link wires for shorts.
5. IF YOU HAVE COMPLETED THE ABOVE and the processor continues to display a peripheral board failure error message, replace that peripheral board.
6. IF THE PROCESSOR DISPLAYS AN ERROR MESSAGE INDICATING THAT THE FIRST BOARD HAS FAILED, check the dip switches on the peripheral boards.
- If the dip switches are incorrect, the board cannot properly communicate with the processor board.
- If two peripheral boards have the same dip switch settings, the peripheral boards will "tie up" the serial link.
Information on the correct dip switch settings can be found on the tags (yelloworange sticker) on the machine. In addition, information on correct dip switch setting is in the schematic book on the tag page. (The black squares on the dip switch symbol on the tag/tag page shows the side of the switch that should be pushed down.)
7. IF THE PROCESSOR DISPLAYS AN ERROR MESSAGE INDICATING THAT THE FIRST BOARD HAS FAILED, unplug the peripheral boards one at a time. If the peripheral boards are wired in a daisy chain fashion, always begin with the last board on the daisy chain. Unplug a board, then turn the machine on. If the processor displays an error that the board just unplugged has failed, replace that peripheral board - it is "tying up" the link. If no error indicating its failures occurs, return the board to its original location and continue this process until the failed board is found.
8. IF ALL PERIPHERAL BOARDS HAVE BEEN UNPLUGGED and the processor continues to show that the first peripheral board that the processor attempts to communicate with has failed, replace the first peripheral board with a known good board with the dip switches set to the correct address. When testing the serial link communications, any peripheral board can be used to test by setting the dip switches on a peripheral board to the address that needs to be tested. For example, if the first board that the processor attempts to communicate with is an 8/16 board and the processor displays that the 8/16 has failed, change any other peripheral board address to the 8/16 board address. Unplug all other peripheral boards, then turn on the machine. If the error changes to the next board that the processor communicates with, the suspect 8/16 board needs to be replaced.
9. IF ALL OF THE ABOVE HAS BEEN ATTEMPTED and the +12 VDC to the processor is good, the +5 VDC to the processor is set from +5.02 to +5.06 using a digital meter, and the processor still displays a peripheral board failure, replace the processor.




dad 04/24/2002
da 2/7/96 id29067