Below is shown the connector pinout:

Table 3. Multifunction connector

Pin

Signal

Function

1

SPKR-

Speaker output

2

SPKR+

Speaker output (+5V)

3

RESET

External reset

4

WDTL

Watch dog timeout latch

5

KBD

Keyboard data

6

KBC

Keyboard clock

7

GND

Ground signal

8

KBP

Keyboard power (+5V)

9

BAT

External Battery input

10

P_B

External Power Button

This section of the connector implements the following functions:

ƒKeyboard

An AT compatible keyboard can be connected to the module through connector J3. The following table lists the pin-out of connector J3.

Table 4.

Pin Signal

5

KBD

6

KBC

7

GND

8

+5V

Keyboard connector

Function

Keyboard data

Keyboard clock

Ground signal

Power supply

ƒSystem reset

Connecting the pin 3 of the multifunction connector to ground performs a hardware reset of the module. It is possible to use an external push-button, normally open. J3 provides a connection for an external normally-open pushbutton to manually reset the system. Connect the other side of the switch to ground. The reset signal is “de-bounced” on the board.

ƒExternal Battery

Pin 9 of the multifunction connector allows the connection of an external backup battery (typically from 3 to 3.9 V). This battery is used at power down to preserve the date-time in the Real Time Clock.

The typical battery consumption with the module off is 7 uA.

ƒSpeaker

A transistor to supply 0.1 watt of power to an external speaker controls these outputs. A transistor amplifier buffers the speaker signal. Use a small general purpose 2 or 3-inch permanent magnet speaker with an 8-ohm voice coil.

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SMC Networks 1232 Series user manual ƒ Keyboard, Pin Signal, +5V, ƒ System reset, ƒ External Battery, ƒ Speaker