Chapter 5 Functional Description

Functional Block Description of the 58502A

Controller Block

This block provides remote instrument management via commands transferred through the RS-232 serial port. It also provides hardware output alarm signals via the Alarm/Status connector that go active when the controller block lights the front-panel system status alarm indicator. Alarm inputs are received and processed by the controller block.

The block consists of a microprocessor and associated support circuitry that together facilitate control of all internal housekeeping, command actions, diagnostic, and system status instrument functions. All instrument functions are controlled and/or monitored by this block.

Panel LEDs Block

This block consists of hardware that provides visual indicators for the operating status of instrument power, system alarm, inputs A and B, and distribution amplifier channels 1 through 12. During normal operation the power, all output status, and one or both input system status indicators should illuminate.

If an effective input signal is lost (absent on both inputs A and B), then both input A and B, and all output status indicators will be extinguished, and the alarm indicator will be lit. If a hardware fault occurs on one or more output distribution channels, then that channel's associated indicator will be extinguished and the alarm indicator will illuminate.

2-to-1 Switch Block

This block consists of inputs A and B routed to a programmable switch that provides a single output to the input of the 1-to-12 Amplifiers and Isolators block. Input selection switching for this block is controlled by the input select line that arrives from the controller block.

The controller block input select line state (at power on from the factory) selects input A over B, if valid signals are present at both connectors, but will switch to input B automatically, if the signal at input A fails. If input B fails and input A signal reappears, the controller block will select input A again as the valid input signal source. If both inputs fail, no select line state change will occur.

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User’s Guide