Micromod MOD: 30ML Installation - Manual (Page 88)

MOD 30ML Multiloop Controller
COMMUNICATIONS CONNECTIONS
RS-485 Cable Requirements
For short runs of 10 to 25 ft (3 to 6m), virtually any 2-wire shielded or twisted pair is suitable.
For runs up to 1000 ft (305 m), Belden 9502 Cable or an equivalent cable is recommended.
This cable is a dual 24 AWG (0.5 mm) twisted pair with an overall foil shield. A drain wire is
provided for grounding the shield. For runs up to 4000 ft (1219.2 m), Belden 9729 Cable or
an equivalent cable is recommended. This cable is a dual 24 AWG (0.5 mm) twisted pair
with a foil shield for each pair. The cable insulation is low dissipation (polypropylene). Two
separate drain wires are provided for grounding the shields
* NOTE: Heavy braid shield cable may be required for certain noisy environments.
Addresses
Each slave on a Modbus network must have a unique address. Addresses 1 through 247 (01
through f7 in hexadecimal) are supported by the Modbus protocol. Addresses for the built-in
circuit are assigned by configuration of a data base attribute. Addresses for modular circuits
are set at the module as shown in Figure 5-7.
Communication Defaults
The 2033N and 2034N RS-485 modules have a COMM DEFAULTS switch which provides
for communication with the module when its configuration is unknown. When the switch is
set at YES, a set of default parameters is invoked. The parameters are: 9600 Baud, no
parity, one stop bit, eight data bits, and the port functionality is slave.
5.5.2 RS-232 Modbus Communication
The built-in and modular circuits for RS-232 communication use a driver/receiver which
supports a point-to-point Modbus network. The modular circuit is contained in a 2033N
communications module. These circuits meet all RS-232C and V.28 specifications. They
have a±9V output swing with a+5V supply, and±30V receiver input levels. All field
connection terminals are optically isolated from the instrument circuitry. The maximum
network cable length is 50 feet.
Both the built-in and modular circuits support the Extended Modbus protocol which provides
full communications functionality between controllers, and between the controllers and any
PC software.
! CAUTION: If the modular communication option is used, be sure the module is
wired properly before applying power. Although this module is isolated,
it can be damaged if excessive voltage is applied across the input pins.
This module is not a drop-in replacement for the ICN module (2030N),
and will be damaged if ICN level voltages are applied to the input pins.
Connections for a typical RS-232 Modbus network using the built-in circuit is shown in Figure
5-4, and connections using the modular circuit are shown in Figure 5-5. Either a computer or
the controller can act as the Modbus master.
82