After investigating the the situation further I find that PIC has
already developed basically what I had in mind. If you download tech note
TBO27 and TBO24 http://www.microchip.com/ you will find the info on 
using flash memory to store the test program. This uses USART2 to download 
the code from a PC serial port. I will use an RS232 switch to switch USART2 
to the GPS when testing the display program.

The C source code boot loader and flash memory programmer software is already 
written and tested and is listed in Tech Note TBO24. It uses the Intel 
Hex 32 Format that comes from the PIC assembler, C compiler and probably 
from the PIC Basic compiler although I am not sure about that.  This 
same format is probably used by the PIC 17C7xx EPROM programmer. 

Is this true Tracy? 

Tracy can also use his EPROM programmer to load the
boot program into the 17C766/CL-ND EPROM section and send the programmed chip
to me. That way I will not have to buy a PIC EPROM burner :-)  

The advantage of flash memory over static RAM is of course you can 
turn the power off and on without losing the downloaded program. This 
has advantages if you would like to test the program in the airplane
rather than just on the bench.

The drawback is the cost for parts is somewhat higher.

I am not going to re-invent the wheel here so I am going to go 
exactly with what PIC recommends. This means a slight redesign of the 
right side of the proto board.

This single chip computer is so powerful with its 16 channel 10 bit 
Analog to Digital converter that eventually we can develop a complete 
EFIS with a large bit mapped LCD  for the rotary engine.

Paul Lamar
 
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