external... ----- Original Message ----- From: "Richard Prosser" To: Sent: Friday, November 08, 2002 12:07 AM Subject: Re: [PIC]: Wierd thing about the 16F628 ??? > But RB4 wouldn't pull low until the program starts - or was it an external > pulldown? > > RP > > > > > It was tied directly to RB4 that was pulled low to avoid entering > programming mode. (Because I didn't need it as an input and the figure in > the programming reference stated taht to enter LVP MCLR and RB4 would rise > to VDD together...) > > This turned out to prevet the circuit from ever starting... very wierd... > > Kyrre > > > ----- Original Message ----- > From: "Olin Lathrop" > To: > Sent: Thursday, November 07, 2002 11:22 PM > Subject: Re: [PIC]: Wierd thing about the 16F628 ??? > > > > > There was something wierd the orther day about my 16F628 based > > prototype... > > > I could simply not get the thing to execute code! > > > After going through all the docs again I still hadn't found what was > > wrong > > > so I did something that shouldn't have solved the issue according to > > specs. > > > I tied MCLR to VDD *even* if it was already tied to VDD internally. > > (Yes, I > > > had disabled it because I didn't need it, and I was using LVP ICSP.) > > > Now, everything worked as it was supposed to? > > > > What were you doing with MCLR before tying it to Vdd, floating? If so, > > that could easly be the problem. MCLR is a CMOS input, which should > never > > be left floating. Any stray noise or static electricity could drive it > in > > any direction. Disabling master clear internally only keeps a low level > > on the MCLR pin from causing a reset. It doesn't mean the MCLR pin is > > driven low (if it was, it would still be useless as an input). Since > MCLR > > has no protection diode to Vdd, it could have picked up noise and driven > > the chip in to high voltage programming mode. > > > > > > ***************************************************************** > > Embed Inc, embedded system specialists in Littleton Massachusetts > > (978) 742-9014, http://www.embedinc.com > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > > > > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu