Download  Print this page

Modbus Function Codes; Supported Function Codes; Read Actual Values Or Settings (function Code 03/04h) - GE B30 Communications Manual

Ur family.
Hide thumbs
   
1
2
Table of Contents
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526

Advertisement

MODBUS FUNCTION CODES

Algorithm
2
2.2 Modbus function codes

2.2.1 Supported function codes

Modbus officially defines function codes from 1 to 127 though only a small subset is generally needed. The relay supports
some of these functions, as summarized in the following table. Subsequent sections describe each function code.
Table 2-4: Function codes
Function code
Hex
Dec
03
3
04
4
05
5
06
6
10
16

2.2.2 Read actual values or settings (function code 03/04h)

This function code allows the master to read one or more consecutive data registers (actual values or settings) from a
relay. Data registers are always 16-bit (two-byte) values transmitted with high order byte first. The maximum number of
registers that can be read in a single packet is 125. See the
registers.
Since some PLC implementations of Modbus only support one of function codes 03h and 04h. The UR interpretation allows
either function code to be used for reading one or more consecutive data registers. The data starting address determines
the type of data being read. Function codes 03h and 04h are therefore identical.
The following table shows the format of the master and slave packets in Modbus RTU. Modbus TCP/IP ADUs have a MBAP
instead of slave address, and CRC is in another stack layer. The example shows a master device requesting three register
values starting at address 4050h from slave device 11h (17 decimal); the slave device responds with the values 40, 300,
and 0 from registers 4050h, 4051h, and 4052h, respectively.
Table 2-5: Master and slave device packet transmission example
Master transmission
Packet format
SLAVE ADDRESS
FUNCTION CODE
DATA STARTING ADDRESS - high
DATA STARTING ADDRESS - low
2-4
1.
FFFF (hex) --> A
2.
0 --> i
3.
0 --> j
4.
Di (+) Alow --> Alow
5.
j + 1 --> j
6.
shr (A)
7.
Is there a carry?
8.
Is j = 8?
9.
i + 1 --> i
10.
Is i = N?
11.
A --> CRC
Modbus definition
Read holding registers
Read holding registers
Force single coil
Preset single register
Preset multiple registers
Example (Hex)
11
04
40
50
No: go to 8; Yes: G (+) A --> A and continue.
No: go to 5; Yes: continue
No: go to 3; Yes: continue
GE Multilin definition
Read actual values or settings
Read actual values or settings
Execute operation
Store single setting
Store multiple settings
Reading PMU records
section on page 2-11 for the data
Slave response
Packet format
SLAVE ADDRESS
FUNCTION CODE
BYTE COUNT
DATA #1 - high
CHAPTER 2: MODBUS COMMUNICATION
Example (Hex)
11
04
06
00
UR FAMILY – COMMUNICATIONS GUIDE

Advertisement

Table of Contents

   Related Manuals for GE B30

This manual is also suitable for:

D30D60F35F60G30G60 ... Show all

Comments to this Manuals

Symbols: 0
Latest comments: