Global Water MODBUS MANUAL For the CL500 Online Residual Chlorine Monitor Global Water 11390 Amalgam Way Gold River CA 95670 Phone: 800-876-1172 Fax: 847-672-9988 EMail:Globalw@globalw.com Website: www.globalw.com Revised (3/09) Rev. 1.
1.0 Overview The Global Water CL500 uses a communication protocol called Modbus. A company called Modicon, for use with their programmable controllers, developed the Modbus protocol. Since that time Modbus has evolved into common communication protocol in industry. The communication method involves using a master-slave technique, in which there is one master and several slaves. The CL500 is a slave device. Only the master can initiate queries.
2.0 Electrical Connections All of the electrical connections to the instrument are made at the termination area, which is located on the portion of the instrument. The connections are labeled and are selfdescriptive (see Figure 1). Please follow all local and government recommendations and methods for installation of electrical connections to and between the instrument and other peripheral devices. Plugs are inserted into cable bulkheads when shipped, to ensure a watertight seal.
2.1 RS-485 Connection The RS-485 half-duplex (2-wire) digital interface operates with differential levels that are not susceptible to electrical interferences. This is why cable lengths up to 3000 ft can be implemented. The last device on every bus may require a 120-ohm termination resistor to eliminate the possibilities of signal reflection on the line. Do not run RS-485 cables in the same conduit as power. Ensure each instrument is not powered when connecting the RS-485 line.
3.0 Operation 3.1 Configuring the RS–485 Port The CL500 is equipped with an RS-485 port which operates in one of three ways (see the operator’s manual for more information). Select the correct baud rate (1200, 2400, 4800, 9600, or 19200) for operation of the I/O port by pressing the t or u buttons to change the displayed baud rate. Press the ↵ button to continue on and select the desired instrument address (1-255) using the t or u buttons. Once the selection is satisfactory, press the ↵ button.
3.1 Configuring the RS–485 Port (continued) For Modbus some applications, especially involving the ASCII operation mode, it may be necessary to set a different protocol than the default setting (8 bits, 1 stop bit, no parity). Menus are available for this in the Extended Settings portion of the configuration CONFIG mode. While in the CONFIG mode, press the ↵ button, several times until the Extended Settings is as shown below. Select On using the t or u buttons.
4.0 The Modbus RS-485 Output & Commands Implemented The default communication parameters are 8 bits, no parity and 1 stop bit. Please note that all Modbus communication is via RS-485. The instruments can support a two wire multidrop network of 255 units. If the connection is to the master on USB, an RS-485 to USB converter is required. 4.1 Coils These single-bit values are readable and changeable from the master. The data will be returned with the lowest addressed coil in the LSB of the data.
4.2 Input Status These single-bit values are readable from the master. The data will be returned with the lowest addressed input status in the LSB of the data. Unused bits in the data will be set to 0. 4.2.1 Valid Command(s) Code Name Broadcast 0x02 Read Input Status No 4.2.2 Format 16-bit word format MSB Bit 15 LSB Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 4.2.3.Valid Addresses 10001 – 10XXX 4.2.
4.3 Holding Registers These 16-bit values are readable and changeable from the master. The data is stored and transmitted with the MSB first and then the LSB. 4.3.1 Valid Command(s) Code Name Broadcast 0x03 Read Holding Registers No 0x06 Preset Single Register Yes 0X16 Preset Multiple Registers Yes 4.3.
Address Type Register Min 40013 Int RS-485 stop bits 0 40014 Int 1 40015 Int 40016 Int Instrument address Modbus serial mode Alarm 1 type 40017, 40018 40019 Float Int 40020, 40021 40022, 40023 40024 40025 Default Max Function 2 -- Odd 0 1 0 – One 1 -- Two 1 255 0 0 1 0 0 2 Alarm 1 set point Alarm 2 type 0.0 0 1.0 0 10.0 2 Float Alarm 2 set point 0.0 1.0 10.0 Int Measurement period Water Conservation 90 150 600 0 0 1 Int 40026 CL500 Modbus (3/09) Rev. 1.
4.4 Input Registers These 16-bit values are readable by the master. The data is stored with the MSB first and then the LSB. 4.4.1 Valid Command(s) Code Name Broadcast 0x04 Read Input Registers No 4.4.2 Format Float – stored in two consecutive addresses, with the first address containing the least significant word (lower part of mantissa) and the second address containing the most significant word (sign, exponent, and upper part of mantissa). 4.4.3 Valid Addresses 30001 – 30XXX 4.4.
30015, 30016 Long 30017, 30018 Long 30019, 30020 Long Level 3 Errors (bit- 0x00000 mapped) 0x00001 0x00002 0x00004 0x00008 0x00010 0x00020 0x00040 0x00080 0x00100 0x00200 0x00400 0x00800 0x01000 0x02000 0x04000 Level 2 Errors (bit- 0x00000 mapped) 0x00001 0x00002 0x00004 0x00008 0x00010 0x00020 0x00040 0x00080 0x00100 0x00200 0x00400 Level 1 Errors (bit0x00000 mapped), most severe 0x00001 0x00002 0x00004 0x00008 0x00010 0x00020 0x00040 0x00080 0x00100 0x00200 CL500 Modbus (3/09) Rev. 1.
Note: Error messages shown in Prentiss and in (Italics) 4.5 Exception Responses Implemented Code 00 01 02 03 Name -ILLEGAL FUNCTION ILLEGAL DATA ADDRESS ILLEGAL DATA VALUE CL500 Modbus (3/09) Rev. 1.3 Meaning No error The function code is not allowed in the device.
