Specifications

Hardware Configuration
2-11
Note
A back-up battery is not needed for storage of the
Configuration Memory parameters.
The real time clock can be backed up with a 3.6V Lithium battery. The Tadiran TL-5242/W is
recommended. It is available from Tadiran Electronic Industries. The backup battery is connected
between J4 pin 9 (+BATV) and J4 pin 2 (-BATV) of the Utility Connector (J4).
2.6 WATCHDOG TIMER
The watchdog timer can be used to trigger a “super-NMI” interrupt, resulting in a system reset,
when it "times out". It is often used at boot time to monitor the boot process. It can also be used to
monitor the activity of an application program. If the application program does not reset the
watchdog timer periodically (because of a malfunction), the watchdog timer will generate a system
reset. To find out more about using the watchdog timer, refer to Chapter 4.
The boot time monitor function is configured in SETUP. This is discussed in Chapter 3. The
application program monitor function must be written into the application. This is discussed in
Chapter 4. In some simple applications, the WATCHDOG program provided on the utility diskette
can be used to retrigger the watchdog timer. Use of the WATCHDOG program is discussed in
Appendix A.
2.7 PERIPHERAL INTERFACE CONFIGURATION AND CONNECTIONS
This section covers the requirements of the board's external device interface connectors.
Information is provided on interface and device characteristics, connector pinouts, signal
definitions, jumper configuration, and nonvolatile Configuration Memory setup.
2.7.1 Utility Connector (J4)
A single 10-pin header connector (J4) provides connections for four functions: speaker, reset,
keyboard, and a "power good" signal. The pinout and signal definitions of the Utility Connector are
shown in Table 2-7. Table 2-8 gives the mating connectors for J4. Here are some considerations
regarding the signals on this connector:
n 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 coil is used.
n A PC compatible keyboard can be connected to the board's keyboard port via connector J4.
Often, keyboards are connected with a 5-pin DIN connector. For convenience, Table 2-9 also
shows the connections for a 5-pin DIN type keyboard connector.