I modified the original AN851 bootloader from 18F8720 to 18F452/18F4520. This is an Quick Programmer in MPLAB.
Original code written by Ross Fosler. Working perfectly! The full programming time 9600baud @4MHz 75secs, 57600baud @20MHz 35secs.
Tested 9600/19200 @4MHZ and @6MHz, 9600/19200/56000/56700 @10MHz-20MHz. All command are working!
The run/program switch is only one button. Entering program mode: first press and hold RESET button than press and hold PROG button, next release RESET than release PROG button. Left program mode: simply press RESET button. Thats it!
Schematic, hex and photos are included.