XA-G49 Datasheet, PDF (13/42 Pages) NXP Semiconductors – XA 16-bit microcontroller family 64K FLASH/2K RAM, watchdog, 2 UARTs

Philips Semiconductors
XA 16-bit microcontroller family
64K Flash/2K RAM, watchdog, 2 UARTs
Preliminary specification
XA-G49
User Supplied Loader
A user program can simply decide at any time, for any reason, to
begin Flash programming operations. All it has to do in advance is to
instruct external circuitry to apply +5V or +12V to the V_PP pin, and
make certain that the Boot ROM is enabled. User code may contain
a loader designed to replace the application code contained in the
Flash memory by loading new code through any communication
medium available in the application. This is completely flexible and
defined by the designer of the system. It could be done serially using
RS-232, serially using some other method, or even parallel over a
user defined I/O port. The user has the freedom to choose a method
that does not interfere with the application circuit. As an added
feature, the application program may also use the Flash memory as
a long term data storage, saving configuration information, sensor
readings, or any other desired data.
The actual loader code would typically be programmed by the user
into the microcontroller in a parallel fashion or via the default loader
during their manufacturing process. The entire initial Flash contents
may be programmed at that time, or the rest of the application may
be programmed into the Flash memory at a later time, possibly
using the loader code to do the programming.
This application controlled programming capability allows for the
possibility of changing the application code in the field. If the
application circuit is embedded in a PC, or has a way to establish a
telephone data link to a user’s or manufacturer’s computer, new
code could be downloaded from diskette or a manufacturer’s
support system. There is even the possibility of conducting very
specialized remote testing of a failing circuit board by the
manufacturer by remotely programming a series of detailed test
programs into the application board and checking the results.
Any user supplied loader should take the watchdog timer into
account. Typically, the watchdog timer would be disabled upon entry
to the loader if it might be running, in order to prevent a watchdog
reset from occurring during programming.
XA Programming Specifications on Philips web site
Programming specifications for the XA family can be located on the
Philips Semiconductors web site at:
www.semiconductors.com/mcu/
Click on Support and Training, then Programming Specifications.
2000 Apr 03
13