Control Circuits - Orban Optimod-FM 8300 Operating Manual

6-6
TECHNICAL DATA ORBAN MODEL 8300
The Output Circuits include the connectors and RF filtering for the analog and digi-
tal audio outputs, and the circuitry to interface the digital processing to these out-
puts.
The DSP Circuits implement the bypass, test tone, and audio processing using digital
signal processing.
The Power Supply provides power for all 8300 circuit sections.
A block diagram of the DSP signal processing appears on page 6-62.

Control Circuits

The control circuit is based on an AMD Elan SC520 microprocessor, which is a 586-
class processor running an Orban executable program over a third-party real-time
operating system. A flash memory emulates a hard drive. The memory is non-volatile
and does not rely on a battery to retain information when mains power is off.
The flash memory holds the operating system, the Orban executable program, and
all preset files, both factory and user. It also contains a write-protected "boot seg-
ment" that functions as a boot ROM.
The control circuits process and execute user-initiated requests to the system. The
source of these requests is the front panel buttons and rotary encoder, the rear
panel RS-232 port, Ethernet port, and the remote contact closures. These changes
affect hardware function and/or DSP processing. The control circuits also send in-
formation to the LCD display.
The control circuit communicates with the DSP and display circuitry through the
SC520's general-purpose bus.
The SC520 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 SC520. 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 finished. If you hear a 30-second audio
mute on air, you can assume that the 8300 has rebooted for some reason. Be pre-
pared to convey this fact to Orban customer service if you call for technical assis-
tance.
The control board is divided into two assemblies: a "base board," which has inter-
face circuitry, and a "CPU controller module," which plugs into the base board and
which contains the CPU, the Ethernet interface chip, the flash memory, the DRAM,
and the real-time clock, which keeps time for the 8300's automation functions. The
real-time clock is backed up by a DL2032 battery so that it keeps accurate time even
when the 8300 is powered down. The battery is socketed and can be readily ac-
cessed by removing the 8300's top cover; the battery is located on the foil (top) side
of the CPU controller module.