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Chapter 3
Utility 1 Interface
The Utility 1 (J15) interface routes various signals to devices such as keyboard, speaker, battery, power-on
LED, and reset switch.
pins, 2 rows, odd/even (1, 2) sequence with 0.100" (2.54mm) pitch and provides the following functions.
Keyboard
The signal lines for a PS/2 keyboard are provided through the Utility 1 interface, which is also fully PC/AT
compatible.
External Battery
An external battery input connection is provided through the Utility 1 interface as well as the J35 header to
support the Real Time Clock in the event the on-board battery is not used.
Power-On LED
The power-on LED signal provides +3.3 volts power for an external LED that indicates the system is
powered on.
Reset Switch
The signal lines for a reset switch are provided through the Utility 1 interface as well as through the J46
Power Button header.
NOTE
To perform the equivalent of a power-on reset, the reset button must be pressed
and held for a minimum of four seconds.
Speaker
The signal lines for a speaker port with 0.1-watt drive are provided through the Utility 1 interface.
Table 3-7. Utility 1 Interface Pin Signals (J15)
Pin #
Signal
1
NC
2
GND
3
NC
4
GND
5
LED
6
NC
7
SPKR+
8
GND
9
RSTSW*
10
NC
11
KBDATA
12
KBCLK
13
GND
14
KBDPWR
30
Table 3-7
defines the pin signals for the J15, Utility 1 header, which consists of 16
I/O
Description
-
Not connected (-12V Power)
-
Ground
-
Not connected (-5V Power)
-
Ground
O
Power-On LED – This on-board +3.3 volts is provided through 330 ohm
resistor to an external Power-On LED.
-
Not connected (Power Good)
O
+ Speaker Output – This signal drives external PC "Beep" speaker.
-
Ground
I/O
Reset Switch – This signal is provided for an external reset switch.
-
Not connected (Keyboard Switch)
I/O
Keyboard Data – Data signal provided to external keyboard connector.
I/O
Keyboard Clock – Clock signal provided to external keyboard connector.
-
Keyboard Ground
-
Keyboard Power – This +5 volts is provided to external keyboard
connector. Requires external fuse for keyboard/mouse protection.
Reference Manual
Hardware
LittleBoard 735
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