IG-267-EN versión 01; 07/04/2017
102
Communications
General Instructions
ekor
.rpa
12. Communications
12.1. Physical medium: RS-485
The physical medium used to establish telecontrol
communications for the
ekor
.rpa-100 series is a twisted pair
cable which connects to the rear RS-485 port (identified as
COM0 and COM1) through an RJ-45 connector.
8
Not used
7
Not used
6
GND
5
485 (-)
4
485 (+)
3
Not used
2
Not used
1
Not used
8
Not used
7
Not used
6
GND
5
485 (-) 485 (1)
4
485 (+)
3
GND
2
485 (-) 485 (2)
1
485 (+)
Figure 12.1.
RS-485
The COM0 is the port used when the unit works as a
telecontrol slave (MODBUS or PROCOME slave).
The communication parameters for the RS-485 COM0 port
can be modified using the user settings. These settings are
classified in the field “
Communications/COM_485
” and are as
follows:
•
Peripheral number
: To set the slave number (from 1 to 99).
•
Bauds
: Transmission speed (1200, 2400, 4800, 9600,
19200 or 38400 bauds).
•
Parity
: Parity (No, Even or Odd).
•
Length
: Length (7 or 8 bits)
•
Stop bits
: Stop bits (1 or 2 bits)
•
Protocol
: Protocol which speaks through report 485
(Cirbus, MODBUS or PROCOME).
The COM1 port is the port used when the unit works as a
MODBUS master for the temperature sensors connected to
the bus. This connection may be carried out in either of the
2 RS-485 ports (can be chosen by configuration) available
in the COM1.
Temperature supervision through the temperature sensors
will only be functional as an option in the
ekor
.rpa-120
models, meaning the COM1 will only apply for these models.
12.1.1. MODBUS protocol
The
ekor
.rpa-100 unit can be configured for the COM0
port communication protocol to be MODBUS. The system
therefore works as a MODBUS slave in RTU transmission
mode (Binary).
The main advantage of this mode over the ASCII mode is
that the information is packed tighter, allowing a higher
data transmission rate at the same communication speed.
Each message is transmitted as a continuous string, as
silences are used to detect the end of the message. The
minimum duration of the SILENCE is 3.5 characters.
RTU message frame
Start
Address
Function
Data
CRC
End
Silence
8 bits
8 bits
n x 8 bits
16 bits
Silence
Table 12.1.
RTU message frame
The MODBUS ADDRESS of the relay (also called peripheral
number) is a byte that takes values between 0 and 99.
The master addresses the slave, indicating its address in the
respective field, and the slave answers by indicating its own
address. The "0" address is reserved for the broadcast mode
so it can be recognised by all slaves.
Summary of Contents for ekor.rpa Series
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