Post by thread:Serial programmer question

Hi, I just built an RS-232 powered 16C84 programmer (the one with 1 diode, 1 cap, 1 78L05, and 3 resistors), but I'm having some problems with it. The 78L05 sucks the tx line (and thus MCLR) down to about 7 volts, which is apparently not enough to kick it into programming mode. I verified this behavior with another 78L05 running on the serial line, driving only a 4.7K resistor + smoothing cap; when nothing is connected to the serial line, I get about 12V on it; when the 78L05 is connected, I get from 5 to 7V depending on the 78L05's load. Am I incorrect in thinking that the '84 needs 12V on MCLR to put it into programming mode? All the other signals to the chip looked fine. Or do I just have a cheesy 78L05? It's made by JRC/NJR. -- Chris Leger (spam_OUTblahTakeThisOuTcmu.edu) Carnegie Mellon University Field Robotics Center

On Fri, 15 Dec 1995, Patrick C Leger wrote: > Hi, > > I just built an RS-232 powered 16C84 programmer (the one with 1 > diode, 1 cap, 1 78L05, and 3 resistors), but I'm having some problems > with it. The 78L05 sucks the tx line (and thus MCLR) down to about 7 > volts, which is apparently not enough to kick it into programming > mode. I verified this behavior with another 78L05 running on the > serial line, driving only a 4.7K resistor + smoothing cap; when > nothing is connected to the serial line, I get about 12V on it; when > the 78L05 is connected, I get from 5 to 7V depending on the 78L05's > load. > > Am I incorrect in thinking that the '84 needs 12V on MCLR to put it > into programming mode? All the other signals to the chip looked fine. > Or do I just have a cheesy 78L05? It's made by JRC/NJR. > It is true the specs call for 12 or 13 Volts on the MCLR pin, but those are the just the specs ;) In reality, the PIC can go into the program mode with much less. I think my serial port surfs on the edge of 7-9 volts during programming. Rather than pulling apart your circuit, you might want to try a serial port on a different computer. -()---()---()---()---()---()---()---()---()---()---()---()---()---()---()- Rolan Yang http://hertz.njit.edu/~rxy5310 Electrical Engineer .....rxy5310KILLspam@spam@hertz.njit.edu kyuriusKILLspamtsb.weschke.com VR,ROBOTICS,FENCING,HACKING,INDUSTRIAL MUSIC,ART,EXPLOSIVES,INLINE SKATING THESE ARE A FEW OF MY FAVORITE THINGS. -()---()---()---()---()---()-----()-()---()---()---()---()---()---()---()- 4 out of 10 people are annoyed by ^ this.

At 18:25 15.12.95 -0500, you wrote: >Hi, > >I just built an RS-232 powered 16C84 programmer (the one with 1 >diode, 1 cap, 1 78L05, and 3 resistors), but I'm having some problems >with it. The 78L05 sucks the tx line (and thus MCLR) down to about 7 >volts, which is apparently not enough to kick it into programming >mode. I verified this behavior with another 78L05 running on the >serial line, driving only a 4.7K resistor + smoothing cap; when >nothing is connected to the serial line, I get about 12V on it; when >the 78L05 is connected, I get from 5 to 7V depending on the 78L05's >load. > >Am I incorrect in thinking that the '84 needs 12V on MCLR to put it >into programming mode? All the other signals to the chip looked fine. >Or do I just have a cheesy 78L05? It's made by JRC/NJR. > I do connect a power supply between 7805 and the diode (I use not a 78l05). Arne -Norway

At 18:25 15.12.95 -0500, you wrote: {Quote hidden}>Hi, > >I just built an RS-232 powered 16C84 programmer (the one with 1 >diode, 1 cap, 1 78L05, and 3 resistors), but I'm having some problems >with it. The 78L05 sucks the tx line (and thus MCLR) down to about 7 >volts, which is apparently not enough to kick it into programming >mode. I verified this behavior with another 78L05 running on the >serial line, driving only a 4.7K resistor + smoothing cap; when >nothing is connected to the serial line, I get about 12V on it; when >the 78L05 is connected, I get from 5 to 7V depending on the 78L05's >load. > >Am I incorrect in thinking that the '84 needs 12V on MCLR to put it >into programming mode? All the other signals to the chip looked fine. >Or do I just have a cheesy 78L05? It's made by JRC/NJR. > >-- >Chris Leger (.....blahKILLspam.....cmu.edu) >Carnegie Mellon University >Field Robotics Center > > I do connect a power supply between 7805 and the diode (I use not a 78l05). Arne -Norway

Patrick C Leger wrote: > > Hi, > > I just built an RS-232 powered 16C84 programmer (the one with 1 > diode, 1 cap, 1 78L05, and 3 resistors), but I'm having some problems > with it. The 78L05 sucks the tx line (and thus MCLR) down to about 7 > volts, which is apparently not enough to kick it into programming > mode. Chris, Check your regulator ...is it really a 78*L*05? It should be just the same size as an ordinary transistor. I built my first PicBlaster with a 7805 (no "L") and had identical results. Make sure you're using the "L"ow-power regulator. -- Rick Miller <http://www.execpc.com/~rdmiller>