MC68HC11A1MFN2 Просмотр технического описания (PDF) - Motorola => Freescale

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MC68HC11A1MFN2

HCMOS Single-Chip Microcontroller

Motorola => Freescale 

2

2.2.4 Additional Boot Loader Program Options

The user may transmit a $55 (only at E clock/16) as the first character rather than the

normal $FF. This will cause the program to jump directly to location $0000, skipping

the download.

The user may tie the receiver to the transmitter (with an external pull-up resistor). This

will cause the program to jump directly to the beginning of EEPROM ($B600). Another

way to cause the program to jump directly to EEPROM is to transmit either a break or

$00 as the first character rather than the normal $FF.

Note that none of these options bypass the security check and so do not compromise

those customers using security.

Keep in mind that upon entry to the downloaded program at location $0000, some reg-

isters have been changed from their reset states. The SCI transmitter and receiver are

enabled which cause port D pins 0 and 1 to be dedicated to SCI use. Also port D is

configured for wired-OR operation. It may be necessary for the user to write to the

SCCR2 and SPCR registers to disable the SCI and/or port D wire-OR operation.

2.2.5 Special Test Operating Mode

The test mode is a special operating mode intended primarily for factory testing. This

mode is very similar to the expanded multiplexed operating mode. In special test op-

erating mode, the reset and interrupt vectors are fetched from external memory loca-

tions $BFC0–$BFFF rather than $FFC0–$FFFF. There are no time limits for protection

of the TMSK2, OPTION, and INIT registers, so these registers may be written repeat-

edly. Also a special TEST1 register is enabled which allows several factory test func-

tions to be invoked.

The special test operating mode is not recommended for use by an end user because

of the reduced system security; however, an end user may wish to come out of reset

in special test operating mode. Then, after some initialization, the SMOD and MDA bits

could be rewritten to select a normal operating mode to re-enable the protection fea-

tures.

MOTOROLA

2-10

SIGNAL DESCRIPTIONS AND OPERATING MODES

MC68HC11A8

TECHNICAL DATA

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