Specifications
Table 2-9. Utility
Connector
(J4)
PIN
SIGNAL
NAME
FUNCTION
1
Audio
return
+5
volts
through
33
ohms
2
Audio
Speaker signel
3
GrOU'ld
To
one
side
of
Reset switch
4
RESET
To
other side of Reset switch
5
LED
Cathode
GrOU'ld
return
6
LED
Anode
Current source
7
GrOU'ld
Grcxnf
return
8
+12V
To
J9
pin
19
9
·5V
To
J9
pin
15
10
·12V
To
J9
pin
17
Speak
..
The
board
provides a
PC
compatible
speaker
output
on
two pins
of
the
Utility
Connector.
The
speaker
signal is
buffered
by
a transistor amplifier
to
provide approximately .1
watt
of
audio power
to
an
external speaker. Typically a small general purpose 2
or
3 inch diameter
permanent magnet speaker with
an
8
ohm
voice coll is used.
Speaker tones can be generated either by directly
"bit~banging"
the speaker control port
or
by
setting
timer
2
to
a desired frequency
tone
and
enabling
the
tone
with
an
enable
port.
See
Chapter 4,
or
a
PC
technical reference manual, for additional programming detaUs.
System Reset
Two pins
of
the Utility Connector provide for the connection
of
an
external
normally~open
momentary switch
to
manually
~ert
a system reset signal.
Power
Indicator
LED
Two pins
of
the. Utility Connector provide for the connection
of
an
external power indicator
LED
device. 15 rnA
of
sourced current is available ( + 5V through 330 ohms).
PC
Bus
Power Option
Five pins
of
the Utility Connector allow the sourcing
of
+ 12VDC,
~5VDC,
and
~12VDC
for
use by devices
connected
to
the
board's
PC
Expansion
Bus
connector
(J9).
The
Little
Board/PC
does
not itself require these voltages.
2~11