Orban OPTIMOD-FM 5518, Operating Manual

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6-6
TECHNICAL DATA ORBAN MODEL 5518

The Input Circuits include the connectors and RF filtering for the analog and
digital audio inputs, as well as the circuitry to interface these inputs to the digi-
tal processing.

The Output Circuits include the connectors and RF filtering for the analog and
digital audio outputs, and the circuitry to interface the digital processing to
these outputs.

The DSP Circuits implement the bypass, test tone, overshoot limiting, and stereo
encoding using digital signal processing.
A block diagram of the DSP signal processing appears on page 6-51.

The Power Supply provides power for all 5518 circuit sections.
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 display circuitry through the SC520’s general-
purpose bus and with the DSP via an SPI serial connection.
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
a second until the DSP code download has finished. If you hear a brief audio mute
on air and you know that its input was not interrupted, you can assume that the
5518 has rebooted for some reason. Be prepared to convey this fact to Orban cus-
tomer service if you call for technical assistance.
The control board contains interface circuitry, the CPU, the Ethernet interface chip,
the flash memory, the DRAM, the RS-232 serial interface circuitry, the GPI/O interface
circuitry, and the real-time clock, which keeps time for the 5518’s automation func-
tions. The real-time clock is backed up by a DL2032 battery so that it keeps accurate
time even when the 5518 is powered down. The battery is socketed and can be
readily accessed by removing the 5518’s top cover; the battery is located on the con-
trol board.