Optimod-AM 9400 V1.2 Operating Manual - Orban

OPTIMOD-AM DIGITAL TECHNICAL DATA 6-5
The drawing on page 6-29 shows circuit board locations.
Overview
The Control Circuits control the DSP, display, and Input/Output sections of the 9400
system.
The Input Circuits include the connectors and RF filtering for the analog and digital
audio inputs, the digital sync input, and the circuitry to interface these inputs to the
digital 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.
The Power Supply provides power for all 9400 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 segment”
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 information
to the LCD display.
The control circuit communicates with the DSP and display circuitry through the
SC520’s ISA 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 9400 has rebooted for some reason. Be pre-