M-BUS nápověda | LG MBUS service tool

M-BUS

Telegrams

During manual diagnostics, the first step is to identify the message type. The first byte usually distinguishes a short frame, long frame, and the single-byte E5 acknowledge.

Single character	Short frame	Control frame	Long frame
E5h	Start 10h	Start 68h	Start 68h
	C field	L field = 3	L field
	A field	L field = 3	L field
	checksum	Start 68h	Start 68h
	Stop 16h	C field	C field
		A field	A field
		CI field	CI field
		checksum	User data
		Stop 16h	(0-252 bytes)
			checksum
			Stop 16h

Single Character

The single E5 byte means acknowledgement without additional data. In diagnostics, it is important to distinguish it from a response that actually contains measured values.

Property	Value and Meaning
Value	`E5h`
Length	`1 Byte`
Typical direction	Slave → Master as acknowledgement of a received command.

RX E5 Single-byte acknowledgement without a data payload.

Short Frame

A short frame has a fixed length and is used for simple control messages. A typical form is 10 C A CS 16, where C is the control field, A is the address, CS is the checksum, and 16 terminates the frame.

Start	C	A	CS	Stop
`10h`	control code	address	`(C+A)mod 256`	`16h`

Element	Decode Check
`10h`	The first byte must be the short-frame start byte. Any other value means another message type or a receive error.
`C`	Defines the procedure, for example SND_NKE, REQ_UD1, or REQ_UD2. Bit meaning is evaluated according to the master/slave direction.
`A`	Must match the target primary address, or a broadcast address according to the request purpose.
`CS`	First only bytes C and A are added, then the lower 8 bits of the result are taken, meaning modulo 256. The start and stop bytes are not included.

TX 10 5B 01 5C 16 Data request to a device with primary address 01.

Control Frame

A control frame uses the 68h start byte but has a fixed length L = 3. It carries only the C, A, and CI fields, meaning control information without user data.

In diagnostics it is used for commands that configure or select a device and do not need to carry measured values.

Start	L	L	Start	C	A	CI	CS	Stop
`68h`	`03h`	`03h`	`68h`	control code	address	application code	`(C+A+CI)mod 256`	`16h`

Use	Technical Meaning
Device selection	The master can use CI and related rules to prepare a slave for further communication without sending measured data in this frame.
Application command without DATA	The frame carries the information in the CI field. Once the command needs parameters or application data, a long frame is used.
Validation	Both L bytes must be 03h, the second start must be 68h, and the checksum is calculated only from C, A, and CI as modulo 256.

TX 68 03 03 68 53 01 51 A5 16 Control frame with fixed length L = 3.

Long Frame

A long frame carries a data payload. A typical form is 68 L L 68 C A CI DATA CS 16. The L pair defines the length from C through the end of data, and CI identifies the application data type.

Start	L	L	Start	C	A	CI	DATA	CS	Stop
`68h`	`L`	`L`	`68h`	control	address	data type	`0-252 Byte`	`(C+A+CI+ΣDATA)mod 256`	`16h`

Validation Step	Rule
Start and length	The first and fourth bytes must be 68h and both L bytes must have the same value.
L range	L includes C, A, CI, and DATA. Therefore a minimum long frame without DATA has L = 3, and each DATA byte increases L by 1.
Checksum	CS is calculated as modulo 256 from the sum of bytes C, A, CI, and all DATA bytes. Start, L, CS itself, and stop are not included.
DATA interpretation	DATA must not be read without CI. CI determines whether the payload is variable data, fixed data, error report, alarm, or another application meaning.

RX 68 15 15 68 08 01 72 78 56 34 12 24 40 01 07 02 00 00 00 04 00 10 27 00 00 38 16 Device response with a variable data header and one data record.

Data Decoding

Decoding proceeds from frame to data: first verify start, length, and checksum, then the C control field, A address, CI field, and finally DIF/VIF data records.

Part	Meaning
`C`	Direction and type of request or response.
`A`	Primary address of the device on the bus.
`CI`	Application data type, for example a variable response with data records.
`DIF/VIF`	Encoding of value, function, meaning, and unit of a data record.

L Field

The L field defines the length of the variable part of a long or control frame. In a long frame, two identical L bytes follow the first 68h start byte, followed by the second 68h start byte.

The L value is counted from the C field through the last DATA byte inclusive. It does not include the 68h start bytes, the L fields themselves, checksum CS, or the 16h stop byte. If the two L values differ, the frame is invalid.

Frame	Form	Meaning of L
Control frame	`68 03 03 68 C A CI CS 16`	Fixed length 3 because the frame contains only C, A, and CI.
Long frame	`68 L L 68 C A CI DATA CS 16`	Variable length of the C, A, CI, and DATA area.

Example	L Calculation
`68 03 03 68 53 01 51 A5 16`	L = 3 because only bytes 53h, 01h, and 51h are counted.
`68 13 13 68 08 05 73 ... CS 16`	L = 13h, meaning 19 bytes from C field 08h through the last payload byte.

During manual decoding, the L field is a good first error filter. If the length is wrong, interpreting DIF/VIF is not useful because a data offset usually breaks the rest of the telegram.

C Field

The C field, also called the Control Field or Function Field, contains the frame control parameters. It defines the data direction and, through the lower function bits, the actual purpose of the message.

In diagnostics, the C field quickly shows whether the frame is an initialization, a write to the device, a data request, or a slave response. In a short frame it follows the 10h start byte; in control and long frames it follows the second 68h start byte. The C field value is included in the checksum.

Direction	7	6	5	4	3	2	1	0
Master → Slave	`0`	`1`	`FCB`	`FCV`	`F3`	`F2`	`F1`	`F0`
Slave → Master	`0`	`0`	`ACD`	`DFC`	`F3`	`F2`	`F1`	`F0`

Bits	Name	Applies To	Communication Meaning
`7-6`	direction pattern	both directions	Value 01b indicates master → slave, value 00b indicates slave → master.
`5`	`FCB / ACD`	by direction	For the master it is the frame count bit; for the slave it is a request to transfer priority Class 1 data.
`4`	`FCV / DFC`	by direction	For the master it validates FCB; for the slave it is data flow control and indicates that the device is not ready to receive more data.
`3-0`	`F3-F0`	both directions	Function code of the procedure, for example initialization, data request, or data response.

In the master → slave direction, the FCB bit alternates between 0 and 1 during error-free communication. If the master does not receive a response to the previous frame, it repeats the same frame with the same FCB and the slave should return the same response again. The FCV bit indicates whether FCB is valid; when FCV = 0, FCB is ignored.

In the slave → master direction, bits 5 and 4 have different meanings. ACD = 1 signals that the slave needs to send priority Class 1 data. DFC = 1 is data flow control: the slave is not ready to accept more data.

Bits F0 to F3 encode the message function itself. The M-BUS data link layer uses two basic procedures: send with confirmation, SND/CON, and request with response, REQ/RSP.

Name	C field bin.	C field hex.	Frame	Description
`SND_NKE`	`0100 0000`	`40`	short	Slave station initialization.
`SND_UD`	`01F1 0011`	`53/73`	long/control	Sending data from the master station to the slave station.
`REQ_UD2`	`01F1 1011`	`5B/7B`	short	Request for regular Class 2 data from the slave station.
`REQ_UD1`	`01F1 1010`	`5A/7A`	short	Request for priority Class 1 data from the slave station.
`RSP_UD`	`00AD 1000`	`08/18/28/38`	long/control	Sending data from the slave station to the master station after a request.

A Field

The A field is the device address on the M-BUS. The master uses it to identify which meter or converter the telegram is addressed to, and the slave returns the same address in its response.

During service diagnostics, the A field is the first place to check whether the configured primary address matches the device response. If the address differs, another device may be responding or the program may use the wrong address.

HEX	DEC	Meaning	Response
`00h`	`0`	Default or unassigned primary device address.	A response is returned if the device uses address 0.
`01h-FAh`	`1-250`	Common primary device addresses in the range 1 to 250.	The device with the matching primary address responds.
`FDh`	`253`	Broadcast for secondary addressing. The specific device is selected by application data, not directly by the A field.	A response is returned by the device selected by secondary address.
`FEh`	`254`	Test broadcast. All devices may respond, so it is mainly used when there is only one device on the bus.	Responses may come from all devices; collisions are likely with multiple devices.
`FFh`	`255`	Broadcast address for a message to all devices without a normal individual response.	No response is returned.

Addressing Mode	What to Check	Service Risk
Primary address 0-250	Match of the A field in request and response, address configuration in the device, and duplicate-address collision.	Two devices with the same primary address can answer simultaneously and corrupt the response.
Secondary addressing through FDh	The device selection is not in the A field itself, but in the application data of the selection telegram.	Without correct secondary-address selection, no device may answer even when it is physically connected.
Broadcast FEh and FFh	Use FEh mainly for testing a single device; FFh is a message to all devices without a normal individual response.	On a bus with multiple devices, FEh can cause response collisions.

TX 10 5B 01 5C 16 The A field is 01h, so the telegram targets the device with primary address 1.

CI Field

The CI field, Control Information, identifies the type of application data in the telegram and the sequence used for the application payload.

For multibyte records, EN1434-3 defines two possible byte orders. The selector is bit 2 of the CI field, counted from bit 0, so the value is 4. This bit is called the M bit or Mode bit.

Mode	M bit	Byte order	Note
Mode 1	`0`	The least significant byte is transmitted first.	Recommended mode for new applications.
Mode 2	`1`	The most significant byte is transmitted first.	Kept for compatibility.

What CI Determines	Decoder Consequence
Application payload type	The same DATA bytes may mean something different depending on CI. After C and A, the decoder must therefore evaluate CI first and only then choose the next parser.
Multibyte value order	The mode bit selects little-endian or big-endian order in application records. Normal new implementations are expected to use Mode 1.
Direction of code usage	Some CI codes are used by the master for write or selection commands, while others are used by the slave in RSP_UD responses. CI must therefore always be read together with the C field.

Codes Used by the Master

Mode 1	Mode 2	Use	Defined in
`51h`	`55h`	Data send.	EN1434-3
`52h`	`56h`	Selection of slaves.	Usergroup July 1993
`50h`		Application reset.	Usergroup March 1994
`54h`		Synchronize action.	suggestion
`B8h`		Set baudrate to 300 baud.	Usergroup July 1993
`B9h`		Set baudrate to 600 baud.	Usergroup July 1993
`BAh`		Set baudrate to 1200 baud.	Usergroup July 1993
`BBh`		Set baudrate to 2400 baud.	Usergroup July 1993
`BCh`		Set baudrate to 4800 baud.	Usergroup July 1993
`BDh`		Set baudrate to 9600 baud.	Usergroup July 1993
`BEh`		Set baudrate to 19200 baud.	suggestion
`BFh`		Set baudrate to 38400 baud.	suggestion
`B1h`		Request readout of the complete RAM content.	Techem suggestion
`B2h`		Send user data, non-standardized RAM write.	Techem suggestion
`B3h`		Initialize test calibration mode.	Usergroup July 1993
`B4h`		EEPROM read.	Techem suggestion
`B6h`		Start software test.	Techem suggestion
`90h-97h`		Codes used for hashing.	obsolete, no longer recommended

Application Reset CI = 50h

CI code 50h lets the master reset the application layer in a slave. After receiving it, the slave decides which parameters to change, for example the default data output. This reset sent as SND_UD with CI = 50h is the application-layer counterpart of the SND_NKE data-link reset.

Optional parameters may follow CI = 50h. The first parameter is an 8-bit application reset subcode: the upper four bits select the telegram type or application, and the lower four bits select the subtelegram number. A zero in the lower four bits requests all subtelegrams.

A slave with only one telegram type may ignore the application reset and the added parameters, but it must acknowledge the command with E5.

Upper 4 bits	Description	Example
`0000b`	All
`0001b`	User data	consumption
`0010b`	Simple billing	actual and fixed-date values including dates
`0011b`	Enhanced billing	historic values
`0100b`	Multi tariff billing
`0101b`	Instantaneous values	regulation
`0110b`	Load management values	management
`0111b`	Reserved
`1000b`	Installation and startup	bus address, fixed dates
`1001b`	Testing	high resolution values
`1010b`	Calibration
`1011b`	Manufacturing
`1100b`	Development
`1101b`	Selftest
`1110b`	Reserved
`1111b`	Reserved

TX 68 04 04 68 53 FE 50 10 B1 16 The master sends an enhanced application reset to all slaves and requests all user-data telegrams.

RX E5 The slave acknowledges the reset with a single E5 byte.

Synchronize Action CI = 54h

CI 54h is intended for synchronization functions in slaves and masters, for example clock synchronization. The other codes listed here are used for baudrate changes, data sending, and slave selection.

Codes Used by the Slave

CI M=0	CI M=1	Use	Defined in
`70h`		Report of general application errors.	Usergroup March 1994
`71h`		Report of alarm status.	Usergroup March 1994
`72h`	`76h`	Variable data response.	EN1434-3
`73h`	`77h`	Fixed data response.	EN1434-3

In practice these codes are interpreted by the response category: fixed data, variable data, general application error, or alarm status.

Fixed Data Structure CI = 73h/77h

The fixed data structure is used in the slave → master direction in a long RSP_UD frame. CI values 73h and 77h tell the decoder that the CI field is not followed by variable DIF/VIF records, but by a fixed block with identification, status, and two counters.

Because the fixed structure can carry only two counters with predefined length and is less descriptive than the variable structure, it is not suitable for new extensible applications. Existing meters still require correct recognition and decoding.

Ident. no.	Access No.	Status	Medium/Units	Counter 1	Counter 2
`4 Byte`	`1 Byte`	`1 Byte`	`2 Byte`	`4 Byte`	`4 Byte`

Field	Coding	Meaning
Identification number	8 packed BCD digits in 4 bytes	Manufacturing or serial number in the range 00000000 to 99999999.
`Access No.`	unsigned binary	Access counter incremented after each RSP_UD response, helping distinguish new data from repeats.
Status	bit flags	Defines counter coding, fixed-date values, and device errors.
Medium/Units	`LSByte first`	Carries the common measured medium and the units of both counters. The lower six bits of each byte define the unit of the corresponding counter, while the upper bits of both bytes together encode the medium.
Counters 1 and 2	`4 Byte`	Values are encoded as BCD or signed binary according to bit 0 in the Status field.

Status Bit	Meaning When 1	Meaning When 0
`0`	Counters are encoded as signed binary.	Counters are encoded as BCD.
`1`	Counters are stored at a fixed date.	Counters are actual values.
`2`	Power low.	Power is not reported low.
`3`	Permanent error.	No permanent error.
`4`	Temporary error.	No temporary error.
`5-7`	Manufacturer-specific meaning.	Manufacturer-specific meaning.

RX 68 13 13 68 08 05 73 78 56 34 12 0A 00 E9 7E 01 00 00 00 35 01 00 00 3C 16 RSP_UD with fixed data structure: address 5, CI 73h, identification number 12345678, two counters.

Variable Data Structure

CI codes 72h and 76h identify a variable data structure in a long RSP_UD frame. After the C, A, and CI fields, the application part starts with a fixed data header and continues with a variable number of data records.

Fixed header 12 Byte Device identification, manufacturer, version, medium, access number, status, and signature.

Data records DIB + VIB + DATA Repeated standard records with their own length, function, unit, and value.

MDH 1 Byte Marks the transition to a manufacturer-specific part when present.

Manufacturer data variable length Area that cannot be reliably interpreted without documentation from the specific manufacturer.

Part	Length	Meaning
Fixed data header	`12 Byte`	Device identification and status information valid for the whole response.
Variable data blocks	variable number	Individual data records in the form DIB, VIB, and data. Each record carries its own length, function, unit, and meaning.
`MDH`	`1 Byte`	The Manufacturer Data Header separates the standard records from the manufacturer-specific part.
Manufacturer-specific data	variable number	Free area defined by the device manufacturer. Without manufacturer documentation it cannot be decoded generically like standard data records.

Fixed Data Header of a Variable Response

The first twelve bytes of user data form a fixed-length block with a fixed field order. The variable data records follow only after this header.

Ident. no.	Manufacturer	Version	Medium	Access No.	Status	Signature
`4 Byte`	`2 Byte`	`1 Byte`	`1 Byte`	`1 Byte`	`1 Byte`	`2 Byte`

Field	Length	Meaning
Identification number	`4 Byte`	In the variable data structure this is a customer number encoded as eight packed BCD digits, so the range is 00000000 to 99999999. It may be preset during production, but it may also be changeable later; if a permanent manufacturing number is needed, it is sent as a separate record, for example DIF = 0Ch and VIF = 78h.
Manufacturer	`2 Byte`	A two-byte unsigned binary value calculated from the three-letter EN 61107 manufacturer ID. Uppercase letters are used and the value is built from the alphabet positions of the letters. `ID = ([ASCII(1) - 64] * 32 * 32)` `+ ([ASCII(2) - 64] * 32)` `+ [ASCII(3) - 64]`
Version	`1 Byte`	Specifies the meter generation or version. The exact meaning depends on the device manufacturer.
Medium	`1 Byte`	Measured medium type. Unlike the fixed data structure, the medium in a variable response is encoded by a full byte.
`Access No.`	`1 Byte`	The access number is an unsigned binary response counter. It is typically incremented after each RSP_UD response and helps distinguish a new response from a repeated one.
Status	`1 Byte`	Status carries the device status bits. In a variable response, the two lowest bits are used to indicate application errors; the remaining bits keep the same meaning as the status flags known from the fixed data structure.
Signature	`2 Byte`	This field is reserved for future encryption applications. When it is not used, it is normally set to 00 00h.

Status bit	Meaning in a Variable Response
`0-1`	Application error or state according to the device specification and related M-BUS rules.
`2`	Low device power.
`3`	Permanent device error.
`4`	Temporary device error.
`5-7`	Manufacturer-specific flags. Without device documentation they should not be interpreted as standard errors.

Header Bytes	Field	Decoded Meaning
`78 56 34 12`	Identification number	Packed BCD number 12345678.
`24 40`	Manufacturer	Two-byte EN 61107 manufacturer code transmitted in the header.
`01`	Version	Meter version or generation according to the manufacturer.
`07`	Medium	Measured medium code.
`02`	`Access No.`	Second response sequence number in the device cycle.
`00`	Status	No standard error signaled by the status flags.
`00 00`	Signature	Signature is not used.

DATA Records

After the fixed 12-byte header, one or more data records follow. Each record is described by its own DIB and VIB blocks; the actual value bytes come only after them.

DIB DIF + DIFE... Describes value format, value function, storage number, tariff, and optional further extension.

VIB VIF + VIFE... Describes quantity, unit, scale, and additional meaning of the value.

DATA 0 to n bytes Contains the actual value. Byte count and coding come from the lower DIF nibble.

DIB	VIB	DATA
`DIF + DIFE...`	`VIF + VIFE...`	value according to DIF

Record part	Length	Meaning
`DIF`	`1 Byte`	The Data Information Field defines the value length and coding, the value function, and whether DIFE follows.
`DIFE`	0 or more bytes	Extends the DIB mainly with additional storage-number and tariff bits. If the extension bit is set in the previous DIF or DIFE, another DIFE follows.
`VIF`	`1 Byte`	The Value Information Field defines the physical quantity, unit, and multiplier of the value. Its extension bit indicates whether VIFE follows.
`VIFE`	0 or more bytes	Extends the VIB with additional unit or value-meaning information. Multiple VIFE bytes may follow according to the extension bits.
`DATA`	according to DIF	The actual value bytes. The byte count and coding are defined by the lower nibble of DIF. The byte order of a multibyte value follows the CI-field mode; new applications use Mode 1, least significant byte first.

DIB and VIB in Detail

A data record is not read by a fixed total record length, but step by step. First the DIB is assembled, then the VIB, and only then the actual DATA value is read according to the lower DIF bits.

Abbreviation	Full name	Contents
`DIB`	Data Information Block	Data information block. It consists of one DIF and optional DIFE bytes.
`DIF`	Data Information Field	First byte of the DIB. It defines DATA coding and length, the value function, the lowest storage-number bit, and whether DIFE follows.
`DIFE`	Data Information Field Extension	Extension of DIF. It adds more storage-number bits, tariff, subunit, and optionally points to another DIFE.
`VIB`	Value Information Block	Value information block. It consists of one VIF and optional VIFE bytes.
`VIF`	Value Information Field	First byte of the VIB. It defines the quantity, unit, value scale, and whether VIFE follows.
`VIFE`	Value Information Field Extension	Extension of VIF. It refines the unit or meaning of the value and may continue with another VIFE.

Data Record Read Order

Step	Part Read	Rule
`1`	`DIF`	Read the first record byte. Special values 0Fh, 1Fh, and 2Fh are handled before normal decoding.
`2`	`DIFE...`	If bit 7 is set in DIF, DIFE follows. If that DIFE also has bit 7 set, another DIFE is read.
`3`	`VIF`	After the DIB is complete, VIF is read to determine the unit and scale of the value.
`4`	`VIFE...`	If bit 7 is set in VIF, VIFE follows. Chaining continues until the last VIFE has bit 7 cleared.
`5`	`DATA`	Finally, the DATA byte count is read according to the lower four DIF bits.

DIF Bit Layout

7	6	5	4	3	2	1	0
DIFE	Storage 0	Function		Data field

Bits	Name	Meaning
`7`	extension bit	Value 1 means that at least one DIFE follows DIF.
`6`	storage number bit 0	Lowest storage-number bit, the first distinction between current and historical values.
`5-4`	value function	Defines whether the value is instantaneous, maximum, minimum, or an error-state value.
`3-0`	data field	Defines the number of DATA bytes and their coding.

DIFE Bit Layout

7	6	5	4	3	2	1	0
DIFE	Subunit	Tariff		Storage

Bits	Name	Meaning
`7`	extension bit	Value 1 means that another DIFE follows.
`6`	subunit	Distinguishes a subunit or meter channel when the device uses it.
`5-4`	tariff	Tariff bits for multi-tariff values.
`3-0`	storage number	Additional storage-number bits. Each additional DIFE adds another four bits.

Result from DIB	Composition	Use During Decoding
Storage number	`DIF bit 6 + DIFE bity 3-0...`	Distinguishes current values, historical values, and other stored value sets.
Value function	`DIF bity 5-4`	Selects instantaneous, maximum, minimum, or error-state value.
Tariff	`DIFE bity 5-4...`	Distinguishes tariff registers in multi-tariff meters.
Subunit	`DIFE bit 6...`	Distinguishes channel, meter part, or subunit when the device uses it.

VIF and VIFE Bit Layout

Field	7	6	5	4	3	2	1	0
`VIF`	VIFE	Quantity, unit, and scale code
`VIFE`	VIFE	Additional VIF code

Field	Bits	Meaning
`VIF`	`7`	Extension bit. Value 1 means that VIFE follows VIF.
`VIF`	`6-0`	Code of the quantity, unit, and value scale, for example energy, volume, flow, temperature, or date.
`VIFE`	`7`	Extension bit. Value 1 means that another VIFE follows.
`VIFE`	`6-0`	Additional code for VIF. It refines the unit, scale, time meaning, or manufacturer-specific value meaning.

Primary VIF - Main Unit Groups

VIF bits 6-0	Quantity	Unit base	Scale
`00h-07h`	Energy	`Wh`	by code in range
`08h-0Fh`	Energy	`J`	by code in range
`10h-17h`	Volume	`m3`	by code in range
`18h-1Fh`	Mass	`kg`	by code in range
`20h-23h`	On time	`s / min / h / d`	unit selected by code
`24h-27h`	Operating time	`s / min / h / d`	unit selected by code
`28h-2Fh`	Power	`W`	by code in range
`30h-37h`	Power	`J/h`	by code in range
`38h-3Fh`	Volume flow	`m3/h`	by code in range
`40h-47h`	Volume flow	`m3/min`	by code in range
`48h-4Fh`	Volume flow	`m3/s`	by code in range
`50h-57h`	Mass flow	`kg/h`	by code in range
`58h-5Bh`	Flow temperature	`°C`	by code in range
`5Ch-5Fh`	Return temperature	`°C`	by code in range
`60h-63h`	Temperature difference	`K`	by code in range
`64h-67h`	External temperature	`°C`	by code in range
`68h-6Bh`	Pressure	`bar`	by code in range
`6Ch`	Date		special date coding
`6Dh`	Date and time		special date-time coding
`6Eh`	HCA units		without physical unit
`70h-73h`	Averaging duration	`s / min / h / d`	unit selected by code
`74h-77h`	Actuality duration	`s / min / h / d`	unit selected by code
`78h`	Fabrication number		identification value
`7Ah`	Bus address		address in data

Special DIF Values

DIF	Meaning
`0Fh`	Start of manufacturer-specific data; the rest of the telegram is no longer read as standard DIF/VIF records.
`1Fh`	Marker that more records follow, typically in another telegram or block.
`2Fh`	Fill byte. It is skipped during decoding and does not represent a data record.

DIF and DATA Length

DIF data field	DATA length	Coding
`0000b / 0h`	`0 Byte`	no data
`0001b / 1h`	`1 Byte`	8-bit integer
`0010b / 2h`	`2 Byte`	16-bit integer
`0011b / 3h`	`3 Byte`	24-bit integer
`0100b / 4h`	`4 Byte`	32-bit integer
`0101b / 5h`	`4 Byte`	32-bit real
`0110b / 6h`	`6 Byte`	48-bit integer
`0111b / 7h`	`8 Byte`	64-bit integer
`1000b / 8h`	`0 Byte`	selection for readout
`1001b / 9h`	`1 Byte`	2 digit BCD
`1010b / Ah`	`2 Byte`	4 digit BCD
`1011b / Bh`	`3 Byte`	6 digit BCD
`1100b / Ch`	`4 Byte`	8 digit BCD
`1101b / Dh`	variable	variable length
`1110b / Eh`	`6 Byte`	12 digit BCD
`1111b / Fh`	special	special functions

Value Function in DIF

Bits 5-4	Function	Meaning
`00b`	instantaneous value	normal current measured value
`01b`	maximum value	stored maximum for the given period or storage
`10b`	minimum value	stored minimum for the given period or storage
`11b`	value during error state	value valid or stored during an error state

Nápověda k protokolu M-BUS