Harris DiamondCD Series, Техническое руководство

Страница: 83 / 256

3/6/08 888-2463-001 4-21
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
Diamond Series™
4.7.2.7 RS-232/RS-485 Interface
To allow a personal computer to be connected at the Cabinet Controller for control of
the transmitter a separate RS-232 line is provided. The Cabinet Controller and the
Module Controllers serial interface output is converted to RS-485 for use in the
transmitter.
The micro processor serial interface output is applied to a level converter/driver U21 to
convert it to RS-485 for use by the PA Modules. This RS-485 communications line is
also converted to serial interface (U20) to be converted to RS-232 by U17 for the
personal computer connection.
4.7.2.8 Xtal
The microprocessor requires a crystal input for operation. Y1 and associated
components provide 4.19 Mhz frequency for the micro.
4.7.2.9 Flash Memory
Fast memory for the microprocessor is furnished by U24 and U34 to allow for field
code updates.
4.7.2.10 Watchdog
The watchdog circuitry will monitor the condition of the microprocessor and will
initialize a software reset if an operations problem occurs.
The micro will output a signal for the watchdog circuit U23-127 (TP35) at least once
every 1.4 seconds. The micro continuously reads the inputs, performs the logic and
protection, writes to the outputs then toggles the watchdog output. If the micro has a
problem completing any of these steps, the watchdog will generate a software reset.
U19 will control the micro reset if the microprocessor locks up, similar to rebooting a
computer. This watchdog reset will also occur after power up.
4.7.2.11 Parallel Control Interface
The ON/OFF control from the GUI and Main Controller enters at J10 pins 1 and 2 and
are opto-isolated by U41 and U43. On board switches (S4, S5) control the cabinet ON/