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Theory of Operation
A4 Comms Assembly
4-8 Agilent E4418B/E4419B Service Guide
A4 Comms Assembly
The comms assembly contains the circuitry required for remote control of
the power meter. This assembly supports parallel and serial interfaces.
The GP-IB interface is supported by a protocol controller integrated
circuit and two physical interface buffers. The system clock is divided by
four to provide the GP-IB controller integrated circuit clock signal.
The RS232 and RS422 interface is supported by a single Universal
Asynchronous Receiver/Transceiver (UART) integrated circuit and a
programmable transceiver. The programmable transceiver can be
configured for either RS232 or RS422. The remote interface is designated
a DTE (Data Terminal Equipment).
The programmable baud rate generator in the UART is driven from the
system clock (16.67 MHz) which allows baud rates in the range 50 to
115.2 K.
The whole assembly is connected to data, address, and control signals
from the A2 processor assembly.
The comms assembly also provides a filtered path for the single/dual
recorder output signal and the TTL input and output signals. It also
provides ESD protection for the RS232.422, TTL I/O, and Recorder
outputs.