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Version 9.1 by Stone Wu on 2022/08/30 09:58
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Leo Wei 1.1 1 The VD2 series servo drive has Modbus communication function, which could cooperate with the host computer for parameter modification, parameter query, monitoring volume servo status query and control. The servo drive is used as a slave device.
2
3 = **Modbus communication** =
4
5 == **Hardware wiring** ==
6
7 The position of RS485 communication port (take VD2B as an example) is as the figure below.
8
Joey 1.2 9 (% style="text-align:center" %)
10 [[image:image-20220608154248-1.png]]
Leo Wei 1.1 11
12 Figure 8-1 The position of RS485 communication port of VD2B drive
13
Stone Wu 8.1 14 For the position of the RS485 communication port of other models, see __[[4.5 Communication signal wiring>>https://docs.we-con.com.cn/bin/view/Servo/Manual/02%20VD2%20SA%20Series/04%20Wiring/#HCommunicationsignalwiring]]__.
Leo Wei 1.1 15
16 The servo drive adopts RS485 half-duplex communication mode. The 485 bus should adopt the hand-in-hand structure instead of the star structure or the bifurcated structure. The star structure or bifurcation structure will produce reflected signals, which will affect the 485 communication.
17
18 (% class="table-bordered" %)
Joey 2.1 19 |(% style="text-align:center; vertical-align:middle" %)[[image:image-20220611153134-1.png]]
Leo Wei 1.1 20 |(((
21 ✎The wiring must use shielded twisted pair, stay away from strong electricity, do not run in parallel with the power line, let alone bundle it together!
22
23 ✎In a half-duplex connection, only one servo drive can communicate with the host computer at the same time. If two or more servo drives upload data at the same time, bus competition will occur. Not only will it lead to communication failure, it may also cause some components to generate large currents and damage the components.
24 )))
25
Joey 1.2 26 (% style="text-align:center" %)
Joey 1.3 27 [[image:image-20220608174415-1.png]]
Leo Wei 1.1 28
29 Figure 8-2 RS485 communication network wiring diagram
30
31 The terminal of RS485 network should use a terminating resistors of 120Ω to weaken the reflection of the signal. Intermediate networks cannot use terminating resistors.
32
33 No point in the RS485 network can be directly grounded. All devices in the network must be well grounded through their own grounding terminals.
34
35 (% class="table-bordered" %)
Joey 2.1 36 |(% style="text-align:center; vertical-align:middle" %)[[image:image-20220611153144-2.png]]
Leo Wei 1.1 37 |Under no circumstances can the grounding wire form a closed loop.
38
39 When wiring, consider the drive capability of the computer/PLC and the distance between the computer/PLC and the servo drive. If the drive capacity is insufficient, a repeater is needed.
40
41 = **Modbus communication protocol analysis** =
42
43 == **Modbus data frame format** ==
44
45 The VD2 series servo drives currently support the RTU communication format. The typical data frame format is shown in the table.
46
47 (% class="table-bordered" %)
Stone Wu 9.1 48 |=(% rowspan="2" scope="row" style="text-align: center; vertical-align: middle; width: 425px;" %)**There should be a message interval not less than 3.5 characters at the beginning**|=(% style="text-align: center; vertical-align: middle; width: 166px;" %)**Address**|=(% style="text-align: center; vertical-align: middle; width: 189px;" %)**Function code**|=(% style="text-align: center; vertical-align: middle; width: 155px;" %)**Data**|=(% style="text-align: center; vertical-align: middle; width: 158px;" %)**CRC check code**
Leo Wei 1.1 49 |(% style="text-align:center; vertical-align:middle; width:166px" %)1 byte|(% style="text-align:center; vertical-align:middle; width:189px" %)1 byte|(% style="text-align:center; vertical-align:middle; width:155px" %)N bytes|(% style="text-align:center; vertical-align:middle; width:158px" %)2 bytes
50
51 == **Description of supported function codes** ==
52
53 The host reads and writes data to the servo through Modbus RTU format (03, 06 function codes). The corresponding Modbus function codes are as follows:
54
55 (% class="table-bordered" %)
Stone Wu 9.1 56 |=(% style="text-align: center; vertical-align: middle;" %)**Operate**|=(% style="text-align: center; vertical-align: middle;" %)**Command code**
Stone Wu 4.7 57 |(% style="text-align:center; vertical-align:middle" %)Read 16-bit/32-bit function code|(% style="text-align:center; vertical-align:middle" %)0x03
Leo Wei 1.1 58 |(% style="text-align:center; vertical-align:middle" %)Write 16-bit function code|(% style="text-align:center; vertical-align:middle" %)0x06
Stone Wu 4.7 59 |(% style="text-align:center; vertical-align:middle" %)Write 32-bit function code|(% style="text-align:center; vertical-align:middle" %)0x10
Leo Wei 1.1 60
Stone Wu 4.7 61 **Read function code: 0x03**
Leo Wei 1.1 62
63 Request format:
64
Stone Wu 4.7 65 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Initial address**|(% colspan="2" %)**Number of reads**|(% rowspan="2" %)**CRC check code**
66 |**high byte**|**low byte**|**high byte**|**low byte**
67 |1 byte|03|1 byte|1 byte|1 byte|1 byte|2 bytes
Leo Wei 1.1 68
69 Correct response format:
70
Stone Wu 9.1 71 (% style="width:1055px" %)
72 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% rowspan="2" style="width:279px" %)**Number of bytes of returned data**|(% colspan="2" style="width:274px" %)**Register 1**|(% rowspan="2" style="width:98px" %)**…**|(% rowspan="2" %)**CRC check code**
73 |(% style="width:160px" %)**high byte**|(% style="width:114px" %)**low byte**
74 |1 byte|03|(% style="width:279px" %)1 byte|(% style="width:160px" %)1 byte|(% style="width:114px" %)1 byte|(% style="width:98px" %)…|2 bytes
Leo Wei 1.1 75
Stone Wu 4.7 76 **Write function code: 0x06**
Leo Wei 1.1 77
78 Request format:
79
Stone Wu 4.8 80 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)(((
81 **Register address**
82 )))|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
Stone Wu 4.7 83 |**high byte**|**low byte**|**high byte**|**low byte**
84 |1 byte|06|1 byte|1 byte|1 byte|1 byte|2 bytes
Leo Wei 1.1 85
86 Response format:
87
Stone Wu 4.8 88 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Register address**|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
Stone Wu 4.7 89 |**high byte**|**low byte**|**high byte**|**low byte**
90 |1 byte|06|1 byte|1 byte|1 byte|1 byte|2 bytes
Leo Wei 1.1 91
92 If the setting is successful, the original is returned
93
Stone Wu 9.1 94 |(% rowspan="2" style="width:551px" %)**There should be a message interval not less than 3.5 characters at the beginning**|(% style="width:114px" %)**Address**|(% style="width:127px" %)**Function code**|(% style="width:104px" %)**Data**|(% style="width:180px" %)**CRC check code**
95 |(% style="width:114px" %)1 byte|(% style="width:127px" %)1 byte|(% style="width:104px" %)N bytes|(% style="width:180px" %)2 bytes
Leo Wei 1.1 96
Stone Wu 4.7 97 (% style="color:inherit; font-family:inherit; font-size:26px" %)**CRC check**
Leo Wei 1.1 98
99 The servo uses a 16-bit CRC check, and the host computer must also use the same check rule, otherwise the CRC check will make mistake. When transmitting, the low bit is in the front and the high bit is at the back. The CRC code are as follows:
100
101 {{code language="LUA"}}
102 {
103
104     Uint16 crc = 0xffff;
105
106     Uint16 i;
107
108
109
110   while(uLen--)
111
112   {
113
114     crc ^=(Uint16) *pBuf++;
115
116     for(i=0; i<8; i++)
117
118     {
119
120       if(crc & 0x0001)
121
122 {
123
124 crc = (crc >> 1) ^ 0xa001;
125
126 }
127
128 else
129
130 {
131
132 crc = crc >> 1;
133
134 }
135
136
137
138     }
139
140   }
141
142   return crc;
143
144 }
145
146 return crc;
147
148 }
149 {{/code}}
150
151 == **Error response frame** ==
152
153 (% class="table-bordered" %)
Stone Wu 9.1 154 |=(% style="text-align: center; vertical-align: middle;" %)**Address**|=(% style="text-align: center; vertical-align: middle;" %)**Function code**|=(% style="text-align: center; vertical-align: middle;" %)**Error code**|=(% style="text-align: center; vertical-align: middle;" %)**CRC check code**
Leo Wei 1.1 155 |(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)Command code+0x80|(% style="text-align:center; vertical-align:middle" %)Error code|(% style="text-align:center; vertical-align:middle" %)2 bytes
156
157 When an error occurs, set the function code bit7 issued by the host to 1, and return (for example, 0x03 returns 0x83, 0x06 returns 0x86); the description of the error code are as follows.
158
159 (% class="table-bordered" %)
Stone Wu 9.1 160 |=(% style="text-align: center; vertical-align: middle;" %)**Error code**|=(% style="text-align: center; vertical-align: middle;" %)**Coding description**
Leo Wei 1.1 161 |(% style="text-align:center; vertical-align:middle" %)0x0001|(% style="text-align:center; vertical-align:middle" %)Illegal command code
162 |(% style="text-align:center; vertical-align:middle" %)0x0002|(% style="text-align:center; vertical-align:middle" %)Illegal data address
163 |(% style="text-align:center; vertical-align:middle" %)0x0003|(% style="text-align:center; vertical-align:middle" %)Illegal data
164 |(% style="text-align:center; vertical-align:middle" %)0x0004|(% style="text-align:center; vertical-align:middle" %)Slave device failure
165
166 == **Communication example** ==
167
168
Stone Wu 4.10 169
170 **03 Function code read**
171
Leo Wei 1.1 172 Read the monitoring volume U0-31 bus voltage, the Modbus register address corresponding to this variable is 7716 (0x1E24)
173
174 Request format:
175
Stone Wu 4.10 176 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Register address**|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
177 |**high byte**|**low byte**|**high byte**|**low byte**
178 |01|03|1E|24|00|01|C2 29
Leo Wei 1.1 179
180 The slave responds normally:
181
Stone Wu 4.10 182 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% rowspan="2" %)**Number of bytes**|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC high byte**
183 |**high byte**|**low byte**
184 |01|03|02|0C|4F|FC B0
Leo Wei 1.1 185
Stone Wu 4.10 186 For example: The value read is 0x0C4F, which means that the voltage is 315.1V.
Leo Wei 1.1 187
Stone Wu 4.11 188
189
Leo Wei 1.1 190 **06 Function Code Write**
191
Stone Wu 4.11 192 P1-10 the maximum speed threshold is set to 3000rpm. This variable corresponds to the Modbus address: 266 (0x010A)
Leo Wei 1.1 193
194 Request format:
195
Stone Wu 4.11 196 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Register address**|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
197 |**high byte**|**low byte**|**high byte**|**low byte**
198 |01|06|01|0A|0B|B8|AF, 76
Leo Wei 1.1 199
200 The slave responds normally:
201
Stone Wu 4.11 202 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Register address**|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
203 |**high byte**|**low byte**|**high byte**|**low byte**
204 |01|06|01|0A|0B|B8|AF, 76
Leo Wei 1.1 205
Stone Wu 4.14 206 **10 Function code write**
207
208 P07-09 set the 1st segment position to 2000, and this variable corresponds to the Modbus address: 1801 (0x0709).
209
210 Request format:
211
212 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Initial address**|(% colspan="2" %)**Number of register**|(% rowspan="2" %)**Number of data**|(% colspan="2" %)**Data 1**|(% colspan="2" %)**Data 2**|(% colspan="2" %)**CRC check code**
213 |**high byte**|**low byte**|**high byte**|**low byte**|**high byte**|**low byte**|**high byte**|**low byte**|**high byte**|**low byte**
214 |01|10|07|09|00|02|04|00|00|07|D0|16|59
215
216 The slave responds normally:
217
218 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Register address**|(% colspan="2" %)**Data**|(% colspan="2" %)**CRC check code**
219 |**high byte**|**low byte**|**high byte**|**low byte**|**high byte**|**low byte**
220 |01|10|07|09|00|02|90|BE
221
Leo Wei 1.1 222 = **Servo communication parameter setting** =
223
Joey 1.2 224 (% style="text-align:center" %)
Joey 1.3 225 [[image:image-20220608174504-2.png]]
Leo Wei 1.1 226
227 Figure 8-3 Modbus communication parameter setting process
228
Stone Wu 9.1 229 **Set the servo address P12-1**
Leo Wei 1.1 230
231 When multiple servos are in network communication, each servo can only have a unique address, otherwise it will cause abnormal communication and fail to communicate.
232
Stone Wu 9.1 233 **Set the serial port baud rate P12-2**
Leo Wei 1.1 234
235 The communication rate of the servo and the communication rate of the host computer must be set consistently, otherwise the communication cannot be carried out.
236
Stone Wu 9.1 237 **Set the serial port data format P12-3**
Leo Wei 1.1 238
239 The data bit check methods of servo communication are:
240
Stone Wu 4.15 241 * Odd parity
242 * Even parity
243 * No parity
244 * The stop bit: 1 stop bit and 2 stop bits.
Leo Wei 1.1 245
246 The data frame format of the servo and the host computer must be consistent, otherwise the communication cannot be carried out.
247
Stone Wu 9.1 248 **Set that whether the function code changed by Modbus communication is written into EEPROM in real time [P12-4]**
Leo Wei 1.1 249
250 When the host computer modifies the servo function code through communication, it can choose to store it in EEPROM in real time, which has the function of power-off storage.
251
252 If the value of the function code only needs to be rewritten once, and the value is used later, the function of real-time writing of the function code to EEPROM can be enabled.
253
254 If you need to change the value of the function code frequently, it is recommended to turn off the function of real-time writing to EERPOM of function code, otherwise the EEPROM will be shortened due to frequent erasing and writing of the EEPROM.
255
256 (% class="table-bordered" %)
Joey 2.1 257 |(% style="text-align:center; vertical-align:middle" %)[[image:image-20220611153214-3.png]]
Leo Wei 1.1 258 |After the EEPROM is damaged, the servo will have an non resettable fault!
259
Stone Wu 9.1 260 **Set the high and low order of the 32-bit monitoring data**
Leo Wei 1.1 261
262 Part of the monitoring volume is 32-bit length and occupies 2 consecutive bias numbers. The user needs to set the order of the data high bit and low bit correctly, otherwise it will cause data reading and writing errors!
263
264 For example, U0-54 (position within 1 circle of absolute encoder) occupies two consecutive offset numbers, which are 0x1E3D and 0x1E3E respectively. Assuming the value of U0-54 is 0x12345678, the correct data sequence bit should be 0x1E3D=0x5678 , 0x1E3E=0x1234 (little endian mode: low byte first, high byte behind.)
265
266 The description of related function codes are as follows.
267
268 (% class="table-bordered" %)
Stone Wu 9.1 269 |=(% style="text-align: center; vertical-align: middle; width: 121px;" %)**Function code**|=(% style="text-align: center; vertical-align: middle; width: 165px;" %)**Name**|=(% style="text-align: center; vertical-align: middle; width: 148px;" %)(((
Leo Wei 1.1 270 **Setting method**
Stone Wu 9.1 271 )))|=(% style="text-align: center; vertical-align: middle; width: 165px;" %)(((
Leo Wei 1.1 272 **Effective time**
Stone Wu 9.1 273 )))|=(% style="text-align: center; vertical-align: middle; width: 109px;" %)**Default value**|=(% style="text-align: center; vertical-align: middle; width: 85px;" %)**Range**|=(% style="text-align: center; vertical-align: middle; width: 224px;" %)**Definition**|=(% style="text-align: center; vertical-align: middle; width: 69px;" %)**Unit**
274 |(% style="text-align:center; vertical-align:middle; width:121px" %)P12-02|(% style="text-align:center; vertical-align:middle; width:165px" %)Baud rate|(% style="text-align:center; vertical-align:middle; width:148px" %)(((
Leo Wei 1.1 275 Operation setting
Stone Wu 9.1 276 )))|(% style="text-align:center; vertical-align:middle; width:165px" %)(((
Leo Wei 1.1 277 Effective immediately
Stone Wu 9.1 278 )))|(% style="text-align:center; vertical-align:middle; width:109px" %)2|(% style="text-align:center; vertical-align:middle; width:85px" %)0 to 5|(% style="width:224px" %)(((
279 * 0: 2400bps
280 * 1: 4800bps
281 * 2: 9600bps
282 * 3: 19200bps
283 * 4: 38400bps
284 * 5: 57600bp
285 )))|(% style="text-align:center; vertical-align:middle; width:69px" %)-
286 |(% style="text-align:center; vertical-align:middle; width:121px" %)P12-03|(% style="text-align:center; vertical-align:middle; width:165px" %)Serial data format|(% style="text-align:center; vertical-align:middle; width:148px" %)(((
Leo Wei 1.1 287 Operation setting
Stone Wu 9.1 288 )))|(% style="text-align:center; vertical-align:middle; width:165px" %)(((
Leo Wei 1.1 289 Effective immediately
Stone Wu 9.1 290 )))|(% style="text-align:center; vertical-align:middle; width:109px" %)0|(% style="text-align:center; vertical-align:middle; width:85px" %)0 to 3|(% style="width:224px" %)(((
291 * 0: 1 stop bit, no parity
292 * 1: 1 stop bit, odd parity
293 * 2: 1 stop bit, even parity
294 * 3: 2 stop bits, no parity
295 )))|(% style="text-align:center; vertical-align:middle; width:69px" %)-
296 |(% style="text-align:center; vertical-align:middle; width:121px" %)P12-04|(% style="text-align:center; vertical-align:middle; width:165px" %)Modbus communication data is written into EEPROM|(% style="text-align:center; vertical-align:middle; width:148px" %)(((
Leo Wei 1.1 297 Operation setting
Stone Wu 9.1 298 )))|(% style="text-align:center; vertical-align:middle; width:165px" %)(((
Leo Wei 1.1 299 Effective immediately
Stone Wu 9.1 300 )))|(% style="text-align:center; vertical-align:middle; width:109px" %)0|(% style="text-align:center; vertical-align:middle; width:85px" %)0 to 1|(% style="width:224px" %)(((
301 * 0: Do not write to EEPROM, and do not store after power failure;
302 * 1: Write to EEPROM, power-down storage.
303 )))|(% style="text-align:center; vertical-align:middle; width:69px" %)-
Leo Wei 1.1 304
305 = **Modbus communication variable address and value** =
306
307 == **Variable address description** ==
308
309 Modbus registers are divided into two categories:
310
Stone Wu 4.15 311 1. The first category is servo function code parameters (address: 0x0001 to 0x0D08), this part of the register is readable and writable (that is, 0x03 and 0x06 are supported);
312 1. The second category is the monitoring volume of the servo (address: 0x1E01 to 0x2010), this part of the register is only readable (0x03 function is supported).
Leo Wei 1.1 313
314 **Servo function code representation: PXX-YY.**
315
Stone Wu 4.15 316 * XX: represents the function code group number,
317 * YY: represents the bias within the function code group;;
Leo Wei 1.1 318
319 During servo communication, the communication address of the function code is a 16-bit address, which is composed of the function code group number (high 8 bits) + group bias (low 8 bits), for example, the Modbus address corresponding to P12-1 (servo address) is 0x0C01.
320
321 **Servo monitor volume representation: Uxx-yy.**
322
Stone Wu 4.15 323 * xx: represents the monitoring volume group number,
324 * yy: represents the bias within the monitoring volume group;
Leo Wei 1.1 325
326 During Modbus communication, the starting address of the monitoring volume is 0x1E01, and the conversion relationship of the address is similar to the representation way of the function code.
327
328 For example, U0-01 (servo status) corresponds to the Modbus address is 0x1E01.
329
330 In order to facilitate actual use, this manual provides both decimal and hexadecimal address identification, it is shown in the following table:
331
332 (% class="table-bordered" %)
Stone Wu 9.1 333 |=(% style="text-align: center; vertical-align: middle; width: 162px;" %)**Function code**|=(% style="text-align: center; vertical-align: middle; width: 302px;" %)(((
334 **Modbus address (Hexadecimal)**
335 )))|=(% style="text-align: center; vertical-align: middle; width: 278px;" %)(((
336 **Modbus address (Decimal)**
337 )))|=(% style="text-align: center; vertical-align: middle; width: 192px;" %)**Category**|=(% style="text-align: center; vertical-align: middle; width: 142px;" %)**Name**
338 |(% style="text-align:center; vertical-align:middle; width:162px" %)P0-1|(% style="text-align:center; vertical-align:middle; width:302px" %)0x0001|(% style="text-align:center; vertical-align:middle; width:278px" %)1|(% style="text-align:center; vertical-align:middle; width:192px" %)Basic settings|(% style="text-align:center; vertical-align:middle; width:142px" %)Control mode
Leo Wei 1.1 339
Stone Wu 7.1 340 For detailed parameter addresses, please refer to __[["11.1 Lists of parameters".>>https://docs.we-con.com.cn/bin/view/Servo/Manual/02%20VD2%20SA%20Series/11%20Appendix/#HListsofparameters]]__
Leo Wei 1.1 341
342 == **Variable value type description** ==
343
344 When writing function codes with signed numbers, you need to convert the pre-written data into hexadecimal complements. The conversion rules are as follows:
345
Stone Wu 4.15 346 1. The data is positive or 0: complement code = original code
347 1. The data is negative: complement code = 0xFFFF-absolute value of data + 0x0001
Leo Wei 1.1 348
Stone Wu 4.15 349 For example:
Leo Wei 1.1 350
Stone Wu 4.15 351 * The 16-bit signed positive number +100, the original code is 0x0064, and the complement is: 0x0064.
352 * The 16-bit signed positive number -100, its hexadecimal complement is: 0xFFFF-0x0064 + 0x0001 = 0xFF9C.
353 * If it is an unsigned number, just pass it directly according to its original code. For example, if the decimal number is 32768, write 0x8000 directly.
Leo Wei 1.1 354
355 == **Numerical unit description** ==
356
357 Some values have units and decimals, such as 0.1%, 0.1Hz, 0.01ms, and the corresponding value conversion is required when reading and writing. The methods are as follows:
358
Stone Wu 4.15 359 1. When the unit is 0.1%: 1 represents 0.1%, 10 represents 1.0%, 1000 represents 100.0%. Therefore, writing 1000 means setting to 100.0%; on the contrary, if it is reading 1000, it means that the value is 100.0%;
Stone Wu 4.16 360 1. When the unit is 0.01ms: 1 means 0.01ms, 50 means 0.5ms, 10000 means 100ms. Therefore, writing 1000 means setting to 10.00ms; on the contrary, if 1000 is read, it means 10.00ms;
361
362 The other units can be deduced by this, and integer remains unchanged.