XA-G49 查看數據表（PDF） - Philips Electronics

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XA-G49

XA 16-bit microcontroller family 64K FLASH/2K RAM, watchdog, 2 UARTs

Philips Electronics 

Philips Semiconductors

XA 16-bit microcontroller family

64K Flash/2K RAM, watchdog, 2 UARTs

Preliminary data

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 +5 V or +12 V to the VPP 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.

2001 Jun 27

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