ABUS Technologies A1500 Universal Process Indicator - Manual (Page 13)

ABUS TECHNOLOGIES INC.
13
A1500
D:
7.2.1 Characteristics
RS-485 compatibility with two-wire connection, from the host is up to 31 slaves in a multi-drop
network topology. And Up to 247 units can be addressed by the MODBUS RTU protocol. Maximum
network distance: 4,000 feet. Time of indicator disconnection: Maximum of 2ms after the last byte. Te
communication signals are electrically isolated from the rest of the instrument, and can be 1200, 2400,
4800, 9600, 19200, 38400, and 57600 bps.
Number of data bits: 8, without parity or pair parity
Number of stop bits: 1
Time to start response transmission: Up to 100ms after acknowledging the command.
Protocol: MODBUS (RTU)
7.2.2 Rs485 Interface: Electrical Connection
RS-485 signals are:
D1= D: Bidirectional data line
D0= Inverted bidirectional data line
C = GND: Ground Optional connection to improve communication performance
Figure 11 shows an example of an RS-485 network. If the computer does not have an RS-485 port
available an external RS232RS485 converter should be used.
Figure 11 - RS-485 network connection