Omega A2400 - Manual (Page 60)

Chapter 10
Transparent Mode
The A2400 is an RS-232/RS-485 converter designed to provide interface
virtually any product to a radio and leased telephone line modems. In normal
operation the A2400 is configured to work on the D series protocol, but it may
be configured to a special communications mode called the transparent
mode. When used in the transparent mode the A2400 module provides an
effective radio or leased-line modem interface for equipment that does not
use the D series protocol.
In normal operation the A2400 communicates with the host on a polling
system; that is, each module responds to its own unique address and must
be interrogated by the host. The microprocessor in the A2400 examines any
character transmitted to it by the host computer. When the microprocessor
detects a valid prompt character ($ or #), it traps the prompt and examines
the next characters for a valid address and a valid command. This simple
command/response protocol must be strictly observed to avoid communi-
cations collisions and data errors.
In the transparent mode the module acts like an open gate for information.
Any data presented at the input to the module will be passed on regardless
of protocol.
A device that is half duplex and uses a 10-bit NRZ asynchronous data format
can be used with the A2400 in the transparent mode. The 10-bit format may
consist of 1 start bit, 7 data bits, 1 parity bit, 1 stop bit or 8 data bits without
the parity bit.
Transparent Mode Functions
In the transparent mode the A2400 provides the user with the following
functions:
1. Ready To Send (RTS) and Clear To Send (CTS) handshaking signals
for RS-232 devices to interface to equipment that require those handshak-
ing signals such as radio or lease-line modems.
2. Networking capability for RS-232 devices by providing unique
channel addressing capability.
3. RS-485/RS-232 conversion for RS-485 devices to interface to
equipment with an RS-232 port such as modems or a host computer.