MX10EXA Просмотр технического описания (PDF) - Macronix International

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MX10EXA

XA 16-bit Microcontroller Family 64K Flash/2K RAM, Watchdog, 2UARTs

Macronix International 

MX10EXA

end-of-file mark. In this application, additional record types

will be added to indicate either commands or data for the

ISP facility. The maximum number of data bytes in a

record is limited to 16 (decimal). ISP commands are sum-

marized in Table 1.

As a record is received by the XA, the information in the

record is stored internally and a checksum calculation is

performed. The operation indicated by the record type is

not performed until the entire record has been received.

Should an error occur in the checksum, the XA will send

an "X" out the serial port indicating a checksum error. If

the checksum calculation is found to match the

checksum in the record, then the command will be ex-

ecuted. In most cases, successful reception of the record

will be indicated by transmitting a "." character out the

serial port (displaying the contents of the internal pro-

gram memory is an exception).

In the case of a Data Record (record type 00), an addi-

tional check is made. A "." character will NOT be sent

unless the record checksum matched the calculated

checksum and all of the bytes in the record were suc-

cessfully programmed. For a data record, an "X" indi-

cates that the checksum failed to match, and an "R"

character indicates that one of the bytes did not prop-

erty program.

The ISP facility was designed so that specific crystal

frequencies were not required in order to generate baud

rates or time the programming pulses.

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 pro-

cess. The entire initial Flash contents may be programmed

at that time, or the rest of the application may be pro-

grammed 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 down-

loaded from diskette or a manufacturer’s support sys-

tem. 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 dis-

abled upon entry to the loader if it might be running, in

order to prevent a watchdog reset from occurring during

programming.

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 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 com-

munication 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 cir-

cuit. 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.

P/N:PM0625 Specifications subject to change without notice, contact your sales representatives for the most update information. REV. 1.0, JUL. 01, 2005

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