A4 Comms Assembly - Agilent Technologies E4416A Service Manual

4 Theory of Operation

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 GPIB interface is supported by a protocol controller integrated circuit and
two physical interface buffers. The system clock is divided by four to provide
the GPIB 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 (20 MHz) which allows baud rates in the range 50 to 20 MHz.
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.
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E4416A/E4417A Power Meters Service Guide