Omega OMEGABUS A2400, User Manual

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Chapter 2
Functional Description
Block Diagram
The A2400 is an RS-232/RS-485 converter specifically designed to inter-
face D series RS-485 modules to radio modems. To this end the A2400
provides three functions:
1) Perform the RS-232 to RS-485 electrical conversion.
2) Control the data direction of the RS-485 bus.
3) Create hand-shaking signals to control the modem.
A simplified block diagram of the A2400 is illustrated in Figure 2.1. This
shows the RS-485 and RS-232 drivers connected to their respective
interface pins. The A2400 contains two UARTs (Universal Asynchronous
Receiver / Transmitters), one dedicated to each port. The RS-485 port is
connected to a UART that is integral to the supervisory microprocessor. The
RS-232 port connects to a second UART external to the microprocessor. All
data communicated to and from the A2400 on either port must pass through
the microprocessor. The micro controls the data flow depending on the
content of the data and setup information specified by the user.
The A2400 contains an Electrically Erasable Programmable Read-Only
Memory (EEPROM) which is used to store operating parameters specified
by the user. The EEPROM will retain the setup data even if power is removed
from the A2400. The EEPROM requires no battery and is guaranteed to
retain data for at least ten years. The setup data stored in the EEPROM
includes the baud rate, address, parity, timing data, etc. When power is
applied to the A2400, the internal microprocessor reads the setup data from
the EEPROM and automatically configures itself. The setup data may be
downloaded with a terminal or computer connected to the RS-232 port.