Control it modbus (rtu) communications option c250 and v250 user guide im/c250–mod_2.
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1 contents 1 introduction ........................................................................................... 2 2 electrical installation ...................................................................... 3 2.1 host computer serial communications ............................................
2 this operating guide describes the commander 250/v250 modbus serial data communications option and must be used in conjunction with the standard user guide (part no. Im/c250 or im/v250) supplied with the instrument. 1 introduction warnings. • if the equipment is used in a manner not specified by t...
3 this section describes the connection of serial data transmission cables between the master (host computer) and slave commander 250/v250 instruments on a modbus serial link. All connections other than those used for serial communication are shown in section 5 of the relevant user guide . 2.1 host ...
4 2.4 pull-up and pull-down resistors – figs. 2.1 and 2.2 to prevent false triggering of slaves when the master (host computer) is inactive, pull- up and pull-down resistors must be fitted to the rs422/485 interface in the host computer – see figs. 2.1 and 2.2. …2 electrical installation fig. 2.2 pu...
5 2.5 termination resistor – fig. 2.3 for long transmission lines, a 120 Ω termination resistor must be fitted to the last slave in the chain – see fig. 2.3. 2.6 serial connections – figs. 2.1 to 2.4 notes. • up to 10 slaves can be connected to a single rs422 adaptor card on a pc. • up to 32 slaves ...
6 notes. • programmable baud rate – 2400 or 9600 baud. • selectable parity – odd, even or none. • address range – 1 to 99. For modbus communications to operate correctly, each commander 250/v250 must be configured with the correct serial transmission parameters and assigned a unique address. 3.1 acc...
7 notes. • the commander 250/v250 operates as a modbus, remote terminal unit (rtu) slave. • parity checking – detects transmission errors in individual characters. • cyclic redundancy checking – detects errors in the master messages and slave responses. • negative numbers are represented in ‘two’s c...
8 4.2 modbus function codes the function code instructs the addressed slave which function to perform. Table 4.1 shows the function codes, and describes the action they initiate. …4 modbus protocol table 4.1 modbus function codes *nak = negative acknowledgment function code function title descriptio...
9 this section shows typical examples of modbus function codes 01, 03, 05, 06, 08 and 16. Not all addressable parameters used in the examples which follow are valid for both instrument types – see sections 7.1 to 7.4. 5.1 read coil status – function code 01 5.1.1 read coil status query this function...
10 5.2 read holding register – function code 03 5.2.1 read holding register query the read holding register query obtains the contents of up to eight holding registers in the addressed slave. Note. The data start register must contain the offset address of the first register to be accessed, e.G. To ...
11 5.3 force single coil – function code 05 5.3.1 force single coil query this message forces a single coil either on or off. The data value 65,280 (ff00 hex) sets the coil on and the value zero turns it off. All other values are illegal and have no effect on coil status. Note. To write to a coil it...
12 5.4 preset single register – function code 06 5.4.1 preset single register query the preset single register query modifies the contents of a holding register. Note. Function codes 05, 06 and 16 are the only messages that are recognized as valid for broadcast. Example. Write the value 500 to holdi...
13 5.5 loopback test – function code 08 5.5.1 loopback test query the loopback test query tests the modbus system and does not affect the operation of the slave. Variations in the response may indicate faults in the modbus system. The information field contains two bytes for the designation of the d...
14 5.6 write multiple registers – function code 16 5.6.1 write multiple registers query this message is used to change the contents of up to eight holding registers at a time. When used with slave address zero (broadcast mode) all slave controllers load the selected registers with the contents speci...
15 the exception response codes sent by the slave are shown in table 6.1. When a slave detects one of these errors, it sends a response message to the master consisting of slave address, function code, error code and error check fields. 6 exception responses 6.1 examples a read register request to r...
16 7 addressable parameters 7.1 commander 250/v250 – coils coil no. Variable label read/write limits/values 01 process variable fail state r 1 = failed 02 remote set point fail state r 1 = failed 03 a/d converter fail state r 1 = failed 06 alarm state 1 r 1 = active 07 alarm indicator 1 r 1 = on 08 ...
17 7 addressable parameters… …7.2 commander 250/v250 – registers 7.2.2 control settings register variable label read/write limits/values 11 process variable input r –999 to 9999 13 control set point r –999 to 9999 14 output 1 rw* –80 to 1100 15 auto/manual state rw 0 = auto; 1 = manual 0 = local 1 =...
18 …7 addressable parameters …7.2 commander 250/v250 – registers 7.2.3 set points register variable label read/write limits/values 40 set point high rw –999 to 9999 41 set point low rw –999 to 9999 42 local set point rw –999 to 9999 43 remote set point input r –999 to 9999 45 fixed set point 1 rw –9...
19 notes.
20 notes.
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Im/c250–mod issue 2 the company’s policy is one of continuous product improvement and the right is reserved to modify the information contained herein without notice. Printed in uk (02.04) © abb 2004 abb limited howard road, st. Neots cambridegshire, pe19 8eu uk tel: +44 (0)1480 475 321 fax: +44 (0)...
