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Chapter 14 - Trouble Shooting and Caring for the QED Board

Trouble Shooting Guide

Before setting up your QED System, we strongly recommend that you read the booklet titled "Getting Started with the QED Board". It contains a wealth of helpful information.

Although we hope your experience with the QED Board will be trouble free, we have anticipated situations which could cause confusion. If after reviewing this chapter you are unable to solve your problem, please feel free to Contact Us.

Symptom: The QED Product Design Kit is turned on, but my display is blank.

Diagnosis: There is nothing wrong; the display is automatically blanked each time the QED Board is turned on.

Solution: Read the "Getting Started with the QED Board" booklet to learn how to write to the display.

Symptom: The QED Board is powered and its communications cable is connected to my terminal, but I get no response from the board at my terminal.

Diagnosis: The three most common reasons for this kind of behavior are:

  1. Power is not being supplied to the QED Board properly.
  2. The communications link between the QED Board and a terminal is improperly configured.
  3. A buggy autostart word or other faulty initialization command has been installed, causing the CPU to crash after every reset.

Solution: Regardless of which diagnosis is correct, in this situation always disconnect power from your QED Board immediately. Once power is no longer connected, the following steps should be taken to identify the problem source.

  1. If your transformer is plugged into an 110 VAC wall outlet, be sure the outlet is working properly. Does a switch control the outlet? Is the switch on? Are all of the plugs in your power bar functioning?
  2. If you are using another type of power source, a regulated +5 VDC or battery, check that it is supplying the appropriate voltage(s) to both the +5V and +5VAN inputs as discussed in Chapter 13. Can the supply source at least 100 milliamps? Are your batteries installed using the appropriate polarity? Is your DC power supply really +5 Volts?
  3. After establishing that your power supply is working properly, examine the power cable connector. Are the appropriate pins on the QED Board power connector attached to the correct voltage rails? Check this carefully by comparing your setup with the diagrams found in the "Power" chapter.
  4. Check that your PC's terminal program is configured to communicate at 9600 baud using 8 data bits, 1 stop bit, 1 start bit, and no parity.
  5. Make sure that the DIP switches on the board are set properly. The best starting configuration is to have all 6 of the DIP switches in the OFF position, with the side of the switch toward the board edge depressed. However, if you have an application PROM installed in socket S3, then switch 3 must be in the ON position.
  6. Check that you are using an appropriate serial communications cable linking your PC to the QED Board. When you purchase your QED Developer Package or QED Product Design Kit, Mosaic Industries provides a serial communications cable that connects to 25 pin IBM-PC compatible serial ports; Apple Macintosh cables are also available from Mosaic Industries. If you have made your own cable, carefully check the connections using the worksheets provided in the Serial Communications chapter in this manual.
  7. If you have an application PROM installed in socket S3 that contains a PRIORITY.AUTOSTART vector, try removing the PROM from the socket. An autostart routine that has a bug in it can cause the processor to continually crash.
  8. If everything mentioned so far is ok and your board still does not respond when power is applied, use the Special Cleanup Mode to completely re-initialize the system software to its "pristine" state. If you have installed a PROM containing an autostart vector in the RAM/ROM socket, remove it. Un-write protect the onboard RAM by turning DIP switches #1 and #2 OFF. To enter the special cleanup mode, turn DIP switch #5 ON and then power up the board or toggle the reset switch (DIP switch #6). The QED-Forth startup message should appear at your terminal. Return DIP switch #5 to the OFF position and execute another reset or power-up to resume normal operation. The special cleanup mode is discussed in the "Interrupts and Register Initializations" Chapter in the Software Manual.

Symptom: The QED Board does not function properly when hardware is interfaced to it via the Address/Data Bus, Digital I/O Bus, Analog I/O Bus, or the Keypad/display bus.

Diagnosis: Disconnect all hardware from the Address/Data Bus, Digital I/O Bus, Analog I/O Bus, and Keypad/display bus. Verify that the board operates properly without this hardware. If it does not, follow the steps outlined above. If it operates properly when it is not connected to the external hardware, then the external hardware is causing the problem.

Solution: Re-connect the external hardware to one bus at a time to isolate the bus connector that is causing the problem. If the QED Board stops functioning when connecting hardware a bus connector, there are several possible explanations:

  1. A control signal is being pulled low by the external hardware. If /IRQ or /XIRQ is being pulled low, the QED Board may be continually interrupted. If /RESET is pulled low, the board will be continually held in the reset condition. If /Shutdown is held low, the main +5V supply will be shut down. All of these signals should normally be in a logical "high" state; check their voltage levels and correct the problem if any of these signals are being held in the low state.
  2. Ensure that the power supplies +5V and +5VAN are not being "dragged down" below their normal 5 Volt levels. Check to be sure that the address/data/page signals and the control signals E, R//W, /RESET, /OE and /WE are not being loaded down by excessive capacitance or very low load resistances. For example, putting standard TTL devices on the bus can place too great a load on the bus signals, which are capable of driving other CMOS and HCMOS devices but not necessarily TTL devices. In this case, replace the offending device or devices with HCMOS-compatible peripherals.
  3. If I/O port bits are being used, check that voltages being applied to inputs do not exceed +5 Volts and do not go below ground in violation of the Motorola specifications.
  4. Check your memory mapped hardware's decode logic. Have you over-mapped areas of memory already in use, leading to contention on the bus? If you are using the QED Protoboard with the address-decoding PAL installed, make sure that its 40 pin connector is connected to the QED Board's address/data bus. If the 40 pin connector on the Protoboard is connected to the Digital I/O bus or the Analog I/O bus, you must remove the Protoboard's PAL from its socket.
  5. If the problem is caused by connecting the keypad/display to the QED Board, make sure that you are using the correct cable and that it is properly connected to the keypad and display. Consult Chapter 10 of this manual for connection instructions.

If you continue having problems after trouble-shooting, contact Mosaic Industries for assistance.


Taking Care of Your Battery-Backed Memory

The QED Board can host battery-backed RAM in the SRAM and SRAM/ROM sockets. Up to 128K can be installed in each of these sockets. Onboard write-protection switches allow you to write protect portions of the memory, providing a means to place your code in "emulated ROM" without actually burning a PROM. To ensure that your write-protected code remains uncorrupted, there are several precautions that should be observed when working with your QED board.

Write protection relies on the logic circuitry's ability to control the special MEM./WE (active-low write enable) signal that controls writes to the onboard memory. If this signal is inadvertently grounded, then the contents of the RAM may be changed even if the DIP switches are set to prevent writes. This special MEM./WE signal is generated by the on-board programmable logic devices and is not brought out to any bus connectors. Thus it is unlikely that the signal could be corrupted. Nevertheless, laying the board flat on a conductive surface or accidentally touching the memory module with a loose ground wire may short this signal to ground and cause loss of the RAM's contents. You would then have to reload your code and data. To avoid this problem, install the board's standoffs as detailed in the "Getting Started with the QED Board" booklet, and use care when handling the board. To avoid "zapping" the board with extremely high voltage static discharge, ground yourself on a metal object before handling the board. Finally, avoid "loading down" the address/data bus with non-HCMOS-compatible peripherals that the processor cannot properly drive. These few simple precautions will ensure reliable operation of your QED Board.

This page is about: Troubleshooting Microcontrollers 68HC11 MC68HC11F1 – Trouble Shooting Guide Before setting up your QED System, we strongly recommend that you read booklet titled Getting Started with QED Board. It contains wealth of helpful information. Although we hope your experience with QED Board will be trouble free, …