Sentinel values for instrumentation
| Size of register
| Sentinel values
| Notes
|
| 16 bit unsigned, any scale
| 0xFFFF
| Unimplemented
|
|
| 0xFFFE
| Over measurable range
|
|
| 0xFFFD
| Under measurable range
|
|
| 0xFFFC
| Transducer fault
|
|
| 0xFFFB
| Bad data
|
|
| 0xFFFA
| High digital input
|
|
| 0xFFF9
| Low digital input
|
|
| 0xFFF8
| Reserved
|
| 16 bit signed, any scale
| 0x7FFF
| Unimplemented
|
|
| 0x7FFE
| Over measurable range
|
|
| 0x7FFD
| Under measurable range
|
|
| 0x7FFC
| Transducer fault
|
|
| 0x7FFB
| Bad data
|
|
| 0x7FFA
| High digital input
|
|
| 0x7FF9
| Low digital input
|
|
| 0x7FF8
| Reserved
|
| 32 bit unsigned, any scale
| 0xFFFFFFFF
| Unimplemented
|
|
| 0xFFFFFFFE
| Over measurable range
|
|
| 0xFFFFFFFD
| Under measurable range
|
|
| 0xFFFFFFFC
| Transducer fault
|
|
| 0xFFFFFFFB
| Bad data
|
|
| 0xFFFFFFFA
| High digital input
|
|
| 0xFFFFFFF9
| Low digital input
|
|
| 0xFFFFFFF8
| Reserved
|
| 32 bit signed, any scale
| 0x7FFFFFFF
| Unimplemented
|
|
| 0x7FFFFFFE
| Over measurable range
|
|
| 0x7FFFFFFD
| Under measurable range
|
|
| 0x7FFFFFFC
| Transducer fault
|
|
| 0x7FFFFFFB
| Bad data
|
|
| 0x7FFFFFFA
| High digital input
|
|
| 0x7FFFFFF9
| Low digital input
|
|
| 0x7FFFFFF8
| Reserved
|
Function 16 - Write Multiple Registers
Writes one or more 16 bit registers to the slave device.
Notes:
1. The limit of 123 registers is to comply with the Modbus specification which requires that a message must not exceed 256 bytes including all fields.
2. A write to a register that is defined in this standard but not implemented on this slave device will return extended exception 4 (Register not implemented) and have no other affect.
3. A write to a register that is defined in this standard as unimplemented will return extended exception 4 (Register not implemented) and have no other affect.
4. A write to a register that is defined in this standard as containing some unimplemented bits will only affect the implemented bits, the state of the unimplemented bits is irrelevant.
5. An attempt to write to a register that is defined as reserved in this standard will return extended exception code 12 (Reserved register) and have no other affect.
6. A write to a multi-register value such as a 32 bit value, a password or a string must be performed by a single message, not by multiple ones. This avoids the possibility of a value being partly current and partly old data.
7. The maximum allowable writing frequency to modbus registers should be limited to 10 times per second, to prolong the life of the module it is recommended that registers are only written to when their value needs to be changed ( avoid writing the same data repeatedly ).
Query message
| Byte
| Field name
| Notes
|
| 0
| Slave address
|
|
| 1
| Function code (16)
|
|
| 2
| First register address - high byte
| 16 bit register address
|
| 3
| First register address - low byte
|
|
| 4
| Number of registers to write - high byte
| 16 bit number of registers, must be in the range 1 to 123
|
| 5
| Number of registers to write - low byte
|
|
| 6
| Byte count (n)
| 8 bit even number in the range 2 to 246 (number of registers *2)
|
| 7
| First register - high byte
| 16 bit register
|
| 8
| First register - low byte
|
|
| …
|
|
|
| 5+n
| Last register - high byte
| 16 bit register
|
| 6+n
| Last register - low byte
|
|
| 7+n/8+n
| Error check CRC
|
|
Normal response message
| Byte
| Field name
| Notes
|
| 0
| Slave address
|
|
| 1
| Function code (16)
|
|
| 2
| First register address - high byte
| 16 bit register address
|
| 3
| First register address - low byte
|
|
| 4
| Number of registers written - high byte
| 16 bit number of registers, must be in the range 1 to 123
|
| 5
| Number of registers written - low byte
|
|
| 6/7
| Error check CRC
|
|
Exception response message
| Byte
| Field name
| Notes
|
| 0
| Slave address
|
|
| 1
| Function code +128 (144)
| Top bit is set
|
| 2
| Exception code
| 1 - Illegal function code
2 - Illegal data address
6 - Slave device busy
|
| 3/4
| Error check CRC
|
|
Language Codes
Notes:
1. Language codes follow the Windows definition, the primary language code is stored in the least significant 10 bits and the sub-language code is stored in the most significant 6 bits of the 16 bit language code.
2. Microsoft add to this list periodically but have reserved sections of the list for custom languages and sub-languages. Primary language codes 0x200-0x3FF can be used for additional languages and sub-language codes 0x20-0x3F can be used for additional dialects of a primary languages but these should only be used where none of the defined codes is appropriate.
Language codes
| Primary language
| Sub-language
| Primary language code
| Sub-language code
| Language code
|
| Neutral
| Neutral
| 0x00
| 0x00
| 0x0000
|
| Arabic
| Saudi Arabia
| 0x01
| 0x01
| 0x0401
|
|
| Iraq
|
| 0x02
| 0x0801
|
|
| Egypt
|
| 0x03
| 0x0C01
|
|
| Libya
|
| 0x04
| 0x1001
|
|
| Algeria
|
| 0x05
| 0x1401
|
|
| Morocco
|
| 0x06
| 0x1801
|
|
| Tunisia
|
| 0x07
| 0x1C01
|
|
| Oman
|
| 0x08
| 0x2001
|
|
| Yemen
|
| 0x09
| 0x2401
|
|
| Syria
|
| 0x0A
| 0x2801
|
|
| Jordan
|
| 0x0B
| 0x2C01
|
|
| Lebanon
|
| 0x0C
| 0x3001
|
|
| Kuwait
|
| 0x0E
| 0x3401
|
|
| United Arab Emerates
|
| 0x0E
| 0x3801
|
|
| Bahrain
|
| 0x0F
| 0x3C01
|
|
| Qatar
|
| 0x10
| 0x4001
|
| Bulgarian
| Standard
| 0x02
| 0x01
| 0x0402
|
| Catalan
| Standard
| 0x03
| 0x01
| 0x0403
|
| Chinese
| Taiwan
| 0x04
| 0x01
| 0x0404
|
|
| Peoples Republic
|
| 0x02
| 0x0804
|
|
| Hong Kong
|
| 0x03
| 0x0C04
|
|
| Singapore
|
| 0x04
| 0x1004
|
|
| Macau
|
| 0x05
| 0x1405
|
| Czech
| Standard
| 0x05
| 0x01
| 0x0405
|
| Danish
| Standard
| 0x06
| 0x01
| 0x0406
|
| German
| Standard
| 0x07
| 0x01
| 0x0407
|
|
| Swiss
|
| 0x02
| 0x0807
|
|
| Austrian
|
| 0x03
| 0x0C07
|
|
| Luxembourg
|
| 0x04
| 0x1007
|
|
| Liechtenstein
|
| 0x05
| 0x1407
|
| Greek
| Standard
| 0x08
| 0x01
| 0x0408
|
Language codes continued
| Primary language
| Sub-language
| Primary language code
| Sub-language code
| Language code
|
| English
| United states
| 0x09
| 0x01
| 0x0409
|
|
| United kingdom
|
| 0x02
| 0x0809
|
|
| Australia
|
| 0x03
| 0x0C09
|
|
| Canada
|
| 0x04
| 0x1009
|
|
| New Zealand
|
| 0x05
| 0x1409
|
|
| Ireland
|
| 0x06
| 0x1809
|
|
| South Africa
|
| 0x07
| 0x1C09
|
|
| Jamaica
|
| 0x08
| 0x2009
|
|
| Caribbean
|
| 0x09
| 0x2409
|
|
| Belize
|
| 0x0A
| 0x2809
|
|
| Trinidad
|
| 0x0B
| 0x2C09
|
|
| Zimbabwe
|
| 0x0C
| 0x3009
|
|
| Philippines
|
| 0x0D
| 0x3409
|
| Spanish
| Traditional
| 0x0A
| 0x01
| 0x040A
|
|
| Mexican
|
| 0x02
| 0x080A
|
|
| Modern
|
| 0x03
| 0x0C0A
|
|
| Guatemala
|
| 0x04
| 0x100A
|
|
| Costa Rica
|
| 0x05
| 0x140A
|
|
| Panama
|
| 0x06
| 0x180A
|
|
| Dominican Republic
|
| 0x07
| 0x1C0A
|
|
| Venezuela
|
| 0x08
| 0x200A
|
|
| Colombia
|
| 0x09
| 0x240A
|
|
| Peru
|
| 0x0A
| 0x280A
|
|
| Argentina
|
| 0x0B
| 0x2C0A
|
|
| Ecuador
|
| 0x0C
| 0x300A
|
|
| Chile
|
| 0x0D
| 0x340A
|
|
| Uruguay
|
| 0x0E
| 0x380A
|
|
| Paraguay
|
| 0x0F
| 0x3C0A
|
|
| Bolivia
|
| 0x10
| 0x400A
|
|
| El Salvador
|
| 0x11
| 0x440A
|
|
| Honduras
|
| 0x12
| 0x480A
|
|
| Nicaragua
|
| 0x13
| 0x4C0A
|
|
| Puerto Rico
|
| 0x14
| 0x500A
|
| Finnish
| Standard
| 0x0B
| 0x01
| 0x040B
|
| French
| Standard
| 0x0C
| 0x01
| 0x040C
|
|
| Belgian
|
| 0x02
| 0x080C
|
|
| Canadian
|
| 0x03
| 0x0C0C
|
|
| Swiss
|
| 0x04
| 0x100C
|
|
| Luxembourg
|
| 0x05
| 0x140C
|
|
| Monaco
|
| 0x06
| 0x180C
|
| Hebrew
| Standard
| 0x0D
| 0x01
| 0x040D
|
| Hungarian
| Standard
| 0x0E
| 0x01
| 0x040E
|
| Icelandic
| Standard
| 0x0F
| 0x01
| 0x040F
|
| Italian
| Standard
| 0x10
| 0x01
| 0x0410
|
|
| Swiss
|
| 0x02
| 0x0810
|
| Japanese
| Standard
| 0x11
| 0x01
| 0x0411
|
| Korean
| Extended Wansung
| 0x12
| 0x01
| 0x0412
|
|
| Johab
|
| 0x02
| 0x0812
|
| Dutch
| Standard
| 0x13
| 0x01
| 0x0413
|
|
| Belgian
|
| 0x02
| 0x0813
|
| Norwegian
| Bokmal
| 0x14
| 0x01
| 0x0414
|
|
| Nynorsk
|
| 0x02
| 0x0814
|
Language codes continued
| Primary language
| Sub-language
| Primary language code
| Sub-language code
| Language code
|
| Polish
| Standard
| 0x15
| 0x01
| 0x0415
|
| Portuguese
| Brazilian
| 0x16
| 0x01
| 0x0416
|
|
| Standard
|
| 0x02
| 0x0816
|
| Rhaeto-romanic
| Standard
| 0x17
| 0x01
| 0x0417
|
| Romanian
| Standard
| 0x18
| 0x01
| 0x0418
|
|
| Moldavia
|
| 0x02
| 0x0818
|
| Russian
| Standard
| 0x19
| 0x01
| 0x0419
|
|
| Moldavia
|
| 0x02
| 0x0819
|
| Croatian
| Standard
| 0x1A
| 0x01
| 0x041A
|
| Serbian
| Latin
| 0x1A
| 0x02
| 0x081A
|
|
| Cyrillic
|
| 0x03
| 0x0C1A
|
| Slovak
| Standard
| 0x1B
| 0x01
| 0x041B
|
| Albanian
| Standard
| 0x1C
| 0x01
| 0x041C
|
| Swedish
| Standard
| 0x1D
| 0x01
| 0x041D
|
|
| Finland
|
| 0x02
| 0x081D
|
| Thai
| Standard
| 0x1E
| 0x01
| 0x041E
|
| Turkish
| Standard
| 0x1F
| 0x01
| 0x041F
|
| Urdu
| Standard
| 0x20
| 0x01
| 0x0420
|
| Indonesian
| Standard
| 0x21
| 0x01
| 0x0421
|
| Ukrainian
| Standard
| 0x22
| 0x01
| 0x0422
|
| Byelorusian
| Standard
| 0x23
| 0x01
| 0x0423
|
| Slovenian
| Standard
| 0x24
| 0x01
| 0x0424
|
| Estonian
| Standard
| 0x25
| 0x01
| 0x0425
|
| Latvian
| Standard
| 0x26
| 0x01
| 0x0426
|
| Lithuanian
| Standard
| 0x27
| 0x01
| 0x0427
|
|
| Classic
|
| 0x02
| 0x0827
|
| Reserved
|
| 0x28
|
| 0x0428
|
| Farsi
| Standard
| 0x29
| 0x01
| 0x0429
|
| Vietnamese
| Standard
| 0x2A
| 0x01
| 0x042A
|
| Reserved
|
| 0x2B
|
| 0x042B
|
| Reserved
|
| 0x2C
|
| 0x042C
|
| Basque
| Standard
| 0x2D
| 0x01
| 0x042D
|
| Sorbian
| Standard
| 0x2E
| 0x01
| 0x042E
|
| Macedonian
| Standard
| 0x2F
| 0x01
| 0x042F
|
| Sutu
| Standard
| 0x30
| 0x01
| 0x0430
|
| Tsonga
| Standard
| 0x31
| 0x01
| 0x0431
|
| Tswana
| Standard
| 0x32
| 0x01
| 0x0432
|
| Venda
| Standard
| 0x33
| 0x01
| 0x0433
|
| Xhosa
| Standard
| 0x34
| 0x01
| 0x0434
|
| Zulu
| Standard
| 0x35
| 0x01
| 0x0435
|
| Afrikaans
| Standard
| 0x36
| 0x01
| 0x0436
|
| Reserved
|
| 0x37
|
| 0x3700
|
| Faeroese
| Standard
| 0x38
| 0x01
| 0x0438
|
| Hindi
| Standard
| 0x39
| 0x01
| 0x0439
|
| Maltese
| Standard
| 0x3A
| 0x01
| 0x043A
|
Language codes continued
| Primary language
| Sub-language
| Primary language code
| Sub-language code
| Language code
|
| Sami (Lapland)
| Standard
| 0x3B
| 0x01
| 0x043B
|
| Scots Gaelic
| Standard
| 0x3C
| 0x01
| 0x043C
|
| Reserved
|
| 0x3D
|
| 0x043D
|
| Malay
| Standard
| 0x3E
| 0x01
| 0x043E
|
|
| Brunei Darussalam
|
| 0x02
| 0x083E
|
| Reserved
|
| 0x3F
|
| 0x043F
|
| Reserved
|
| 0x40
|
| 0x0440
|
| Swahili
| Standard
| 0x41
| 0x01
| 0x0441
|
| Reserved
|
| 0x42-0x1FF
|
|
|
| Custom languages
|
| 0x200-0x3FF
|
| 0x0200-0x03FF
|
| Custom language
| English for pumps
| 0x20
| 0x00
| 0x0200
|
Modbus Registers Defined
Notes:
1. The register array is divided into 256 pages each containing up to 256 registers, the actual register address is obtained from the formula: register_address=page_number*256+register_offset.
2. All unused parts of pages 0-127 are defined as reserved for expansion of this standard, any attempt to access them will result in an exception response with extended exception code 12 (Reserved register).
3. Pages 128-255 are available for manufacturer specific applications such as configuration of the control equipment, these are not defined by this standard.
4. Any device which requires registers in pages 128-255 to be implemented in order to perform a task which can be performed by registers defined in this standard is deemed to be non-compliant with this standard.
5. This document always refers to register addresses which start at 0 as defined in the Modbus protocol. Register numbers, which start at 1, are not used in this document in order to avoid confusion.
6. The additional instrumentation pages are to be defined.
7. S.M. means state machine.
8. A letter S in the bits/sign column indicates a signed value using two’s compliment arithmetic, all others are unsigned.
9. A double number in the bits/sign column indicates a bit within a register of a specific size e.g. 16/16 is the most significant bit and 1/16 is the least significant bit of a 16 bit register.
10. Bits within registers are numbered from 1 not 0 to avoid the confusion that would be caused if the sixteenth bit of a 16 bit register were labelled 15/16.
11. For an integer type register the register contents should be multiplied by the scaling factor to obtain the actual value.
12. For a flag type register (1 bit) the minimum value column indicates the meaning if the flag is 0, the maximum column indicates the meaning if the flag is 1.
13. For an integer type register the minimum and maximum value columns indicate the minimum and maximum values after multiplying by the scaling factor.
14. Any software that reads an integer type register must be able to process and display correctly over the full range specified in the minimum and maximum value columns.
15. 32 bit values are stored with the most significant bits in the register with the lowest address.
16. Where two ASCII characters are stored in a single register the first character is in the most significant bits.
17. The first register of a 32 bit number is always aligned at an even address for the benefit of some 32 bit CPUs.
Index of Register Pages
| Page number
| Description
| Read/write
|
| 0
| Communications status information
| Read only
|
| 1
| Communications configuration
| Read/write and write only
|
| 2
| Modem configuration
| Read/write
|
| 3
| Generating set status information
| Read only
|
| 4
| Basic instrumentation
| Read only
|
| 5
| Extended instrumentation
| Read only
|
| 6
| Derived Instrumentation
| Read only
|
| 7
| Accumulated Instrumentation
| Read/write
|
| 8
| Alarm conditions
| Read only
|
| 9
| Total Harmonic Distortion information
| Read only
|
| 10
| Reserved
|
|
| 11
| Diagnostic - general
| Read only
|
| 12
| Diagnostic - digital inputs
| Read only
|
| 13
| Diagnostic - digital outputs
| Read only and read write
|
| 14
| Diagnostic - LEDs
| Read only and read write
|
| 15
| Diagnostic - Reserved
|
|
| 16
| Control registers
| Read only and write only
|
| 17
| J1939 active diagnostic trouble codes in decoded format
| Read only
|
| 18
| J1939 active diagnostic trouble codes in raw format
| Read only
|
| 19
| Reserved
|
|
| 20
| Various strings
| Read only
|
| 24
| Identity strings
| Read/write
|
| 26
| State machine name strings
| Read only
|
| 28
| State machine state strings
| Read only
|
| 29-31
| Reserved
|
|
