I use Philips ISP FLASH products.

In my company's product, we stream out telemetry information over a serial link to a PC during normal operation. Our PC display & analysis software includes special software for downloading our new hex files (we don't ship that feature to customers and it requires an attached programmer card of mine).

I flip a toggle switch on the attached programmer card and it places the microprocessor in ISP download mode. The PC then grabs the latest 8051 hex file and downloads it serially into the 8051 over the very same cables used for telemetry. We never have to touch the cable. The Philips micro even handles the baud matching.

Could it be any easier? Yes, but we'll not reveal that. :-)

When we are ready to ship a unit, we use the same serial link to burn a fuse-flag preventing the FLASH from being read or reprogrammed ever again.

Why is FLASH better than OTP? You can download self-calibration routines and test routines as the electronics progresses down the assembly line fixtures. We also include some application software as payload inside our 8051 that runs on other platforms (we don't have to include diskettes with the software). Being able to change that for particular customers is quite useful.

-Jay C. Box