Tadpole SPARCbook 3 series, Reference Manual

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12-4
Microcontroller Subsystem
Microcontroller subsystem overview
12.1.2 Internal keyboard scanning
The microcontroller address bus signals are driven out to the internal
keyboard drive lines and depressed keys are sensed via the data bus. The
microcontroller implements debounce and key repeat control in software.
12.1.3 External keyboard and mouse
The microcontroller subsystem incorporates a dual universal asynchronous
receiver transmitter (DUART). This handles serial transfers and from the
keyboard and mouse ports on the baseboard.
Input from the internal and external mouse and internal and external
keyboards is multiplexed by the microcontroller. This allows internal
devices to remain active while an external mouse and/or keyboard are
connected.
12.1.4 Pointing stick
The pointing stick uses strain gauge technology to detect and quantify
vertical and horizontal pressure. It produces two outputs (for the x and y
directions) which are amplified by a high-gain amplifier before being
applied to analog-to-digital converters in the microcontroller. The dc bias
of the amplifiers is software adjustable via a digital potentiometer, allowing
pointing stick recalibration and sensitivity adjustment to be carried out in
software.
12.1.5 Real time clock
The real time clock is used solely to provide the timed “wake up” alarm; a
facility that allows the user to set (via the NCE Save Panel, see the NCE
User Guide) a time at which the SPARCbook 3 system powers up
automatically. All accesses to this real time clock are handled by the
microcontroller in response to commands from the host.
The microconroller subsystem’s real time clock is in addition to the
MK48T08 real time clock which is fitted to the base board. The latter is
used by the OpenBoot firmware as in a conventional SPARCstation.
12.1.6 EEPROM
The EEPROM is used to store system manufacturing information. The
EEPROM is a serially accessed device which is read and written using its
own command set. Commands are written to it along with any new data via
D(0). Data is read from the device via D(1).
S3GX_TRMBook Page 4 Friday, September 19, 1997 11:39 am