A4 Comms Assembly - Keysight Technologies E4417A 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.
92 Keysight E4416A/E4417A Power Meters Service Guide