Overview; Control Circuits - Orban OPTIMOD-FM 5500 Operation Manual

6-6
TECHNICAL DATA

Overview

Control Circuits


The Control Circuits control the DSP, display, and input/output sections of the
5500 system.

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, and audio processing using
digital signal processing.
A block diagram of the DSP signal processing appears on page 6-51.

The Power Supply provides power for all 5500 circuit sections.
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
5500 has rebooted for some reason. Be prepared to convey this fact to Orban cus-
tomer service if you call for technical assistance.
ORBAN MODEL 5500