Watkins-Johnson Company WJ-8718A/MFP Instruction Supplement page 111

CIRCUIT DESCRIPTION
3.4.1. 7.14 Received Data (RxD)
WJ-8718A/MFP
The serial data stream on the RxD input to the USART contains the instructions
from the remote control equipment. The data word is an ll-bit character consisting of a start
bit, a parity bit (if parity is enabled), eight data bits, and a stop bit. Data format is discussed in
paragraph 2.4.5. Figure 3-12 illustrates a remote controller with three receivers under control.
Circuits equivalent to the repeater networks in the receiver illustrate the flow of receive and
transmit data through the receivers. The logic levels are based on the assumption that
receiver 3 is the addressed unit. Logic gates in the repeater network invert the logic sense of
received data between the USART and the RS-232/C bus. The gates also switch signal levels
between TTL and 232 logic.
3.4.1. 7.15 Transmitted Data (TxD)
The information on the TxD line is a serial data stream transmitted from the
USART to the remote control equipment. The data comprises current receiver parameters as
requested by the controller. See paragraph 2.4.5 for information about data format.
Figure 3-12 illustrates the flow of transmit data through a controlled network of three
receivers. The circuits in the illustration are representative of the repeater network which
assures the integrity of the data signals. The logic gates in the repeater network invert the
logic sense of transmitted data between the USART and the RS-232/C bus. The gates also
s wi tch signal levels between TTL and 232 logic.
3-56