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Discussion Groups | 68HC12 | MC912D60A question
Join our technical discussions about Freescale Microcontrollers: M68HC12. (Freescale Semiconductor is a Subsidiary of Motorola).
MC912D60A question - Alar Lepp - Jul 26 10:56:00 2002
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Hi all! Has anybody experience with such a strange behaviour of MC912D60ACPV8, mask 2K38K: I have two identical boards with D60A (single-chip mode). Both are at permanent reset state caused by D60A RESET pin. Level of reset signal are 0.7 V at one board and almost 0V on another board with pull-up 4.7 k. When decreasing pull-up to 1k parallel to 4.7k on 1-st board then RESET level increases till 2.3V, then pulses sporadically between 2.3 and 5V. Power supply and GND connections, also clock frequency and stability (PLL not used - VDDPLL and XFC pins are grounded) seemed to be OK (ceramic resonator frequency 4.915 MHz). Effect is the same booting in normal or special mode. I have used D60 (not D60A) and B32 before, without any such effects. Strange is also fact that in some very really rare cases CPU starts OK. Of course after some time (usually after RESET command from BDM) things are going wrong again. Alar |
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RE: MC912D60A question - Kelley, Dale - Jul 26 14:32:00 2002
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Can you try driving it will TTL clock? sounds like the OSC takes too long to get
stable Dale Kelley -----Original Message----- From: Alar Lepp [mailto:] Sent: Friday, July 26, 2002 11:57 AM To: Subject: [68HC12] MC912D60A question Hi all! Has anybody experience with such a strange behaviour of MC912D60ACPV8, mask 2K38K: I have two identical boards with D60A (single-chip mode). Both are at permanent reset state caused by D60A RESET pin. Level of reset signal are 0.7 V at one board and almost 0V on another board with pull-up 4.7 k. When decreasing pull-up to 1k parallel to 4.7k on 1-st board then RESET level increases till 2.3V, then pulses sporadically between 2.3 and 5V. Power supply and GND connections, also clock frequency and stability (PLL not used - VDDPLL and XFC pins are grounded) seemed to be OK (ceramic resonator frequency 4.915 MHz). Effect is the same booting in normal or special mode. I have used D60 (not D60A) and B32 before, without any such effects. Strange is also fact that in some very really rare cases CPU starts OK. Of course after some time (usually after RESET command from BDM) things are going wrong again. Alar -------------------------------------------------------- To unsubscribe from this group, send an email to: To learn more about Motorola Microcontrollers, please visit http://www.motorola.com/mcu |
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Re: MC912D60A question - Doron Fael - Jul 28 2:02:00 2002
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Alar, Are you sure connecting XFC to GND is allowed? I thought XFC should be left floating if the internal PLL is not used. Also I am not sure what is the maximum allowed frequency to use a ceramic resonator. With a crystal I think it is either 4MHz or 8MHz, and I think it is lower with a ceramic resonator. I would try just for experiments a lower frequency crystal (say 1MHz). The D60A (and other HC12 derivatives) is using a Colpitt crystal, for reduced voltage swing (a few hundreds mili Volts only). The down side of this, is that often there are clock startup problems at this configuration, especially at relatively high clock rates, and when the resonator or crystal is not physically located right next to the HC12. Doron HC12 In Circuit Emulators Nohau Corporation www.nohau.com At 06:56 PM 7/26/2002 +0300, you wrote: >Hi all! > >Has anybody experience with such a strange behaviour of MC912D60ACPV8, mask >2K38K: >I have two identical boards with D60A (single-chip mode). Both are at >permanent reset state caused by D60A RESET pin. Level of reset signal are >0.7 V at one board and almost 0V on another board with pull-up 4.7 k. When >decreasing pull-up to 1k parallel to 4.7k on 1-st board then RESET level >increases till 2.3V, then pulses sporadically between 2.3 and 5V. >Power supply and GND connections, also clock frequency and stability (PLL >not used - VDDPLL and XFC pins are grounded) seemed to be OK (ceramic >resonator frequency 4.915 MHz). Effect is the same booting in normal or >special mode. I have used D60 (not D60A) and B32 before, without any such >effects. >Strange is also fact that in some very really rare cases CPU starts OK. Of >course after some time (usually after RESET command from BDM) things are >going wrong again. > >Alar > >-------------------------------------------------------- >To unsubscribe from this group, send an email to: >To learn more about Motorola Microcontrollers, please visit >http://www.motorola.com/mcu [Non-text portions of this message have been removed] |
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Re: MC912D60A question - Oliver Betz - Jul 29 2:46:00 2002
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Doron Fael <> wrote: > Are you sure connecting XFC to GND is allowed? I thought XFC should be > left floating if the internal PLL is not used. It is allowed but makes no sense IMHO. > Also I am not sure what is the maximum allowed frequency to use a > ceramic resonator. This depends on the series resistance of the resonator and the load capacitance. > With a crystal I think it is either 4MHz or 8MHz, The docs say nothing (16MHz), Gordon Doughman says 8MHz. My measurements say: with a good crystal 16MHz is possible, but with 50Ohms crystal ESR and a weak D60A it could fail. A pullup resistor can cure the problem but I can't suggest to run the D60A without PLL. > and I think it is lower with a ceramic resonator. I would try just for No reason for this assumption. AFAIK there are resonators with better ESR specs than cheap crystals. > experiments a lower frequency crystal (say 1MHz). > > The D60A (and other HC12 derivatives) is using a Colpitt crystal, for > reduced voltage swing (a few hundreds mili Volts only). The down side > of this, is that often there are clock startup problems at this > configuration, especially at relatively high clock rates, and when the > resonator or crystal is not physically located right next to the HC12. The distance is unlikely a problem unless you put it really far away. The problem is that you have to optimize load capacitance to get as much amplitude with the sparse bias current supplied by the D60A. Oliver |
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Re: MC912D60A question - r52590 - Jul 29 4:40:00 2002
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Hi, I have been facing a same problem for this, in which the reset still always stay at low for HC912B32. I check for my configuration, seems ok, Vdd is 5V, Gnd is 0v, except that my voltage output for ocillatior is about 2.5V for high and 0V for low. The oscilator frequency is 16Mhz. The HC12 will reset if the frequency clock level is undetermine (refer to it manual book). I suspect my voltage output for oscilator is not high enough, and the MCU assume the 2.5V as at the middle range of high and low, hence can not determine the clock level. What I try back by using a generator to generate out 8Mhz of clock cycle with 5V at high level, the reset will not stay at low but always 5V. Just have a look at your voltage level of the clock. Regards Loke Sheng > > Has anybody experience with such a strange behaviour of MC912D60ACPV8, mask > 2K38K: > I have two identical boards with D60A (single-chip mode). Both are at > permanent reset state caused by D60A RESET pin. Level of reset signal are > 0.7 V at one board and almost 0V on another board with pull-up 4.7 k. When > decreasing pull-up to 1k parallel to 4.7k on 1-st board then RESET level > increases till 2.3V, then pulses sporadically between 2.3 and 5V. > Power supply and GND connections, also clock frequency and stability (PLL > not used - VDDPLL and XFC pins are grounded) seemed to be OK (ceramic > resonator frequency 4.915 MHz). Effect is the same booting in normal or > special mode. I have used D60 (not D60A) and B32 before, without any such > effects. > Strange is also fact that in some very really rare cases CPU starts OK. Of > course after some time (usually after RESET command from BDM) things are > going wrong again. > > Alar |
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