OPTIMOD-FM TECHNICAL DATA
6-7
A block diagram of the DSP signal processing appears on page 6-44.
Control Circuits
The control circuit is based on an Elan SC400 microprocessor, which is a 486-class proc-
essor running an Orban executable program over a third-party real-time operating system.
A disk-on-chip memory emulates a hard drive. The memory is non-volatile and does not
rely on battery back-up to retain information when mains power is off.
The disk-on-chip holds the operating system, the Orban executable program, and all pre-
set files, both factory and user. There is also a boot ROM that allows the microprocessor
to start up before control is handed to the operating system.
The control circuits process and execute user-initiated requests to the system. The source
of these requests is the front panel buttons, joystick, and rotary encoder, the rear panel
RS-232 ports, and the remote contact closures. These changes affect hardware function
and/or DSP processing. The control circuits also send information to the quarter-VGA
passive-matrix color LCD display.
The control circuit contains a real-time crystal-controlled clock to keep time for the
8400’s automation functions. It is backed up by a DL2032 battery so that it keeps accu-
rate time even when the 8400 is powered down.
The control circuit communicates with the DSP and display circuitry through the Elan’s
ISA bus.
The Elan periodically refreshes a watchdog timer. If the timer times out without being
refreshed, it assumes that the control program has crashed and automatically reboots the
Elan. The DSP chips will continue to process audio until the time comes to reload DSP
program code into them. At this point, the audio will mute for about 30 seconds until the
DSP code download has been completed. If you hear a 30-second audio mute on air, you
can assume that the 8400 has rebooted for some reason. Be prepared to convey this fact
to Orban customer service if you call for technical assistance.
User Control Interface and LCD Display Circuits
The user control interface enables the user to control the functionality of the 8400 unit. A
rear panel GPI connector implements optically isolated remote control of certain func-
tions, such as recalling presets. Two RS232 serial ports allow you to connect a modem or
computer to the 8400. Front panel pushbutton switches and a joystick select between
various operational modes and functions.
1. Remote Interface and RS-232 Interfaces
Located on control board
A remote interface connector and circuitry implements remote control of certain operat-
ing modes; Model 8400 OPTIMOD-FM has eight remote contact closure inputs.
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