I have updated the WLoader bootloader design at
http://www.xs4all.nl/~wf/wouter/pic/wloader/index.html WLoader now occupies
the top 1K (was 2K) and the hardware uses a MAX232.

A bootloader is a piece of code, mostly used in a 16F877, that allows the
downloading of an application to the 16F877 without any programming hardware
(other than the hardware for the communication). The WLoader page contains
more explanation about bootloaders (versus other ways of programming), and
links to the other bootloaders that I know of. WLoader is a bit special
among the bootloaders because it takes more code (some others are only 256
instructions) but it can use any one (!) pin for the communication and
activation.

Wouter van Ooijen

Van Ooijen Technische Informatica: http://www.voti.nl
Jal compiler for PIC uC's:  http://www.xs4all.nl/~wf/wouter/pic/jal

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.