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908QB8 programming
Dane H. Nov 16, 2016 at 08:32 AM (08:32 hours)
Staff: Johnny N.

  • We are having to buy brokered parts for the obsolete 908QB8 and are having trouble programming some using the cyclone pro. Is it possible that some of these have been previously programmed in such a way that they cannot be reprogrammed? The parts marked M(or S)08QBCDTE or 08QBMDTE communicate fine and can be programmed. The parts marked M08QBCTG won't establish baud rate to start the programming process, either with a sap file in the cyclone pro or using the HC08 programming app on the PC. Investigating handshake signals reveal good parts will show 8 volts on the IRQ/HV pin, but only 5 volts (TST voltage being clamped to Vcc?) on this pin on bad parts. Any ideas? Thanks for your help.


    • Hi Dane,

      For the QB8 and most other HC08 devices, entering monitor mode requires the Vtst on IRQ if the vector addresses $FFFE and $FFFF are not blank ($FF).

      Are these devices on a board or are they stand alone? If they are on a board, it is possible that the designer clamped IRQ to 5V as a security measure. Tf these parts were previously programmed, then I don't believe it is possible for a proper handshake to occur to enter monitor mode on them.

      CAn you de-solder the chip and install them on a "good" board?


  • Actually these are loose parts that I connected to the Cyclone box with a TSSOP zif socket. We usually are able to program these on board in our board test fixture, but when this issue came up I created this chip fixture for research. So there is no clamp on IRQ. So do you believe these can be originally programmed in such a way as to not be able to be reprogrammed? We are able to reprogram good ones many times even after they have been soldered onto our assemblies. 
    Thanks for your help.

    • Dane,

      I have not heard of a way to program these devices that would permanently prevent monitor mode entry or that would clamp Vtst to 5V.

      You can try disconnecting IRQ from the Cyclone Pro and applying Vtst directly to the pin when it is required. Just run the MON08 Diagnostics mode in our PROG08SZ software and it will go through the process step by step.


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