Modbus - CIAT AirControl CTA Manuel De Régulation

5.3 ModBus

5.3.1 ModBus RTU connection diagram
5.3.2 RS485 connection close-up
The components required for connection to the remote and/or local ModBus supervision system are as follows:
- An RS485 serial card (CIAT code: 7119749) connected to each controller.
- A standard RS485/USB converter for connection to a PC (not supplied by CIAT). The converter can be connected to any network
RS485 card.
- An electrical network using an AWG20/22 shielded cable (not supplied by CIAT) comprising a twisted pair and shielding with a
max length of 1000 m. This network must never run parallel to power cables at a distance of less than 50 cm. These cables may
cross, but perpendicularly. You are requested not to form a loop with the network cable or the earth braid, and to properly separate
the various cable families (control, power, earth and communication bus).
- A supervision program installed on a PC (not supplied by CIAT).
A 120Ω ¼W electrical heater must be connected to the RS485 serial card in last position on the bus, as shown in the connection
diagram.
The format of the data frame, which cannot be modified, is as follows: 8 data bits, 2 stop bits and without parity on 2 words (2
bytes), high-order, low-order.
The data format (16 bits, signed) is standard for ModBus except for analogue data which is in the format "Integer divided by 10"
Pin Description
1 GND
2 RX+/TX+
3 RX-/TX-
EN - 45
EN