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Hi all, Does anyone know if while the HC11 (the 68HC11E0 in particular) is running in expanded mode, and the XIRQ input(which also happens to be Vpp for the E series and I suspect for the E0 also, despite that the E0 doesn't have any available internal EPROM, it apparently is the same circuit) rises momentarily to above Vdd (due to some signal spike), could this possibly cause the HC11 to go nuts? If so, is this associated with the dual role of XIRQ as Vpp or it would happen to any input pin? I searched for app notes and other documentation at Motorola but didn't find anything related to this. I know about the normal operational ranges of input pins, but what I need to know is whether the XIRQ pin in particular (which by design can handle higher voltages) can cause the MCU to misbehave (please remember I'm talking about expanded mode, so program execution is not from internal memory)? Thanks for your responses.

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Tony -- That's a stumper here. If I had to face the problem without factory help, I would probably build a test fixture and try to reproduce the problem. As I recall, the Vpp voltage doesn't go anywhere until the 'Enable' bit is set in the programming register (EEPGM in PPROG) and then, you can't even set EEPGM unless EELAT was set earlier. See the (White)Pink book, Section 4.5.4. But before going to that trouble, I would try submitting the question to the Motorola help email box as a new Service Request. Best wishes, Bob Smith --- Avoid computer viruses, Practice safe hex --- -- Specializing in small, cost effective embedded control systems -- Robert L. (Bob) Smith Smith Machine Works, Inc. 9900 Lumlay Road Richmond, VA 23236 804/745-1065 ----- Original Message ----- From: "Tony Papadimitriou" <> To: <> Sent: Wednesday, February 19, 2003 2:35 PM Subject: [m68HC11] XIRQ going above Vdd but not for programming > Hi all, > > Does anyone know if while the HC11 (the 68HC11E0 in particular) is running > in expanded mode, and the XIRQ input(which also happens to be Vpp for the E > series and I suspect for the E0 also, despite that the E0 doesn't have any > available internal EPROM, it apparently is the same circuit) rises > momentarily to above Vdd (due to some signal spike), could this possibly > cause the HC11 to go nuts? If so, is this associated with the dual role of > XIRQ as Vpp or it would happen to any input pin? > > I searched for app notes and other documentation at Motorola but didn't find > anything related to this. > > I know about the normal operational ranges of input pins, but what I need to > know is whether the XIRQ pin in particular (which by design can handle > higher voltages) can cause the MCU to misbehave (please remember I'm talking > about expanded mode, so program execution is not from internal memory)? > > Thanks for your responses. > To unsubscribe from this group, send an email to:

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