AN1796 Datasheet, PDF (1/17 Pages) STMicroelectronics – FIELD UPDATES FOR FLASH BASED ST7 APPLICATIONS USING A PC COMM PORT

AN1796
APPLICATION NOTE
FIELD UPDATES FOR FLASH BASED ST7 APPLICATIONS
USING A PC COMM PORT
by Dennis Nolan
INTRODUCTION
Having the capability to update software in a microprocessor while the part remains in-circuit
has proven to be a very valuable feature of the new flash based micro controllers. Generally,
this has been accomplished via a special dedicated connector (something like a 10 pin
header) on the board which talks to a specialized programmer which, in turn, is controlled by
a PC. While the cost of these programmers has come down steadily, mostly due to increased
capabilities of the MCUs to virtually program themselves, they are still not very available to the
end user. The purpose of this note is to present practical software techniques which can be
built into virtually any application which includes an RS232 serial port to allow the flash based
ST7 MCU to be updated by any end user in the field.
The software presented here is a small (less than 500 bytes) boot loader which will allow for
the operating software in the ST7 to be replaced safely and reliable by use of a standard S-
Records format file which can either be emailed to an end user or made available for download
on a Web site. The PC side of the software update operation can easily be accomplished
using any of a number of terminal emulation programs. In this note the operation will be de-
scribed using the HyperTerminal program which is available to all Windows based PC users
since it comes bundled with the operating system.
AN1796/1103
Rev. 1.0
1/17
1