I've done some general search here but couldn't find anything that put me on track, so...

I'm using an AT89C51AC2, programming with Keil uVision 3 in C.

Usually I program these with Flip in-house, but I have been asked to upgrade the application to allow the chips to be updated on the road though a serial interface.

As far as I can tell, I have 2 choices:

1) Change the hardware to allow a controller unit to speak to specific units in turn (I have 9 chips in each unit all on the same RS485 line), and then write an application that automates, & copies what Flip does.

2) Create a bootloader that can be triggered by the controller so the chips program themselves.


With option 2 I have some questions about the fundamentals of bootloaders...


1) I believe that using a bootloader I get the application to program the 2K On-Chip Bootloader Flash and trigger a reset.

Does this mean I can only upload 2k of data at a time? As the application is around 20k this doesn't seem a good way of doing things.

2) Is it possible to create a bootloader application that can receive it's code via the RS485 line? Would this be automated with API's, or can I use my own addressing scheme to receive data and place it into the main Flash memory?

3) With each update, I would need to be able to program 9 different chips (all AC2's). I presume that I would need to program each one in turn, but all would be sitting on the same 485 line. Would this cause any obvious problems?


As you can see, my knowledge on bootloaders & IAP is a little limited, and so far, I haven't found much info that explains how to go about things.