Re: [avr-gcc-list] avrdude, ATMega128

[Anton Erasmus]

On 5 Jun 2005 at 14:45, Torsten Mohr wrote:

> Hi,
> 
> > > The supply voltages look ok.
> > > PEN is connected to GND.
> >
> > This should be VCC. Not even JTAG programming works if this is GND.
> 
> i just soldered some additional capacitors to the pcb i made.  Just
> when i did this, the wire that held PEN to GND fell off.
> 
> Now the program works and i see 2.5 V with the DMM on Port B (as
> expected) and i see the expected pattern on port D.
> 
> Also, i soldered the additional capacitors off again and now it also
> works, i can erase and reprogram the device.
> 
> I see two possibilities now:
> 
> 1. PEN has to be left open (i understand the data sheet differently)
> 
> 2. when i soldered the SMD capacitors i had bad contact on some pads
> and
>     i fixed that when i soldered the additional capacitors.
> 
> 
> Any way, i wonder now why i can erase and reprogram the device even
> with PEN left open.  According to the data sheet there is an internal
> pull-up and PEN needs to be pulled low during reset.  On the PCB, PEN
> is now open and by that pulled high during reset.  I measure 5V at
> PEN.
> 

The way I interpret the stuff regarding PEN in the manual is that it's status is
latched at a reset. If high then one can program the device. If held low at 
reset,
then it cannot be reprogrammed until it has been reset again. 

Regards
  Anton Erasmus-- 
A J Erasmus