Danfoss M-Bus Operating guide

1	Basic information ....................................................................................................			4
	1.1	The physical layer .............................................................................................		4
	1.2	Wake up process and baud rate changes (IR) .......................................................		4
	1.3	Baud rate changes ............................................................................................		4
	1.3.1		Wait time before reply after correct message reception....................................	5
	1.4	Data Link layer (DLL).........................................................................................		5
	1.4.1		C field (Control field, Function field) – Field size 1 byte ...................................	5
	1.4.2		A Field (Address Field) – 1 byte ....................................................................	6
	1.4.3		L Field – 2 fields with a size of 1 byte ............................................................	7
	1.4.4		CS field – 1 byte .........................................................................................	7
	1.5	Combined Transportation and application layer .....................................................		8
	1.5.1		CI Field (Control information field) ................................................................	8
	1.5.2		Long header ...............................................................................................	9
	1.5.3		Status byte and error handling ...................................................................	10
	1.5.4		DIF & VIF configuration of data records........................................................	11
	1.6	The standard read out .....................................................................................		13
2	Communication process .........................................................................................			16
	2.1	M-Bus EN 13757 data frames ...........................................................................		16
	2.2	Pulse readout .................................................................................................		17
	2.3	Application reset .............................................................................................		17
	2.4	Send/Confirm procedures available using the Danfoss Meter.................................		21
	2.4.1		SND_NKE .................................................................................................	21
	2.4.2		SND_UD ..................................................................................................	22
	2.4.3		REQ_UD2 .................................................................................................	34
	2.4.4		RSP_UD ...................................................................................................	35
Annex A		.....................................................................................................................		36

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Identify the needed telegrams from the EN13757 standard and determine how to implement the SonoSelect 10 and SonoSafe 10 communication protocol into an M-Bus telegram. This document contains the description the M-Bus protocol implemented for SonoSelect 10 and SonoSafe 10. The M-Bus protocol will follow the EN13757 standard.

According to the software architecture of the SonoSelect 10 and SonoSafe 10 the communication shall be split into three layers.

Figure 1 - OSI model and architecture of HM

The M-Bus protocol for the IR and Wired communication will be identical and therefore these two components will share the same data-link and application layer. The M-Bus will only support physical, data-link and combined transportation and application layer. The other layers stated in EN13757-3 are optional and will not be part the wired M-Bus implementation of the SonoSelect 10 and SonoSafe 10. According to the EN13757-1 standard the transportation layer must be handled in an Application Layer.

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The physical layer is a serial asynchronous half-duplex communication.

The meter act as a slave and each character communicated consist of 11-bits as shown below:

•1 start bit (‘Space’)

•8 data bits

•1 parity bit (even)

•1 stop bit (‘Mark’)

The master issues a request and the slave respond.

Since the optical interface uses the EN 13757-2 protocol, a wake-up message can be sent after every ¡die time of> 330 bit times to the heat meter. The wake up message consists of zeroes and ones alternating at the desired baud rate for a duration of (2,2 ± 0,1) s. After an idle time of 33 bit times to 330 bit times, the communication can start.

The baud rate requirements from EN13757-3 are as follows:

•The IR supports 2400 and 4800 Baud

•The wired baud rate supports 300, 2400, 4800 and 9600

•Baud rate is kept after reset of device.

Meters with hardware issue 5 have auto baudrate detection on both the IR and Wired M-Bus interface.

Maximum data records:

The maximum data record length is 235 bytes

Wildcard search (Secondary address)

Secondary address is found by using a wildcard search (CI = 52H). The top positions are run through in ten selections from 0-9 (0FFFFFFF – 9FFFFFFF). If slave is found it answers with an ACK and the master requests the full secondary address which is returned in a RSP_UD from the slave. Any collisions and the master vary the next positions and hold the existing one.

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After reception of valid telegram the slave has to wait between 11bit time and (330 bit times + 50ms) before answering (EN1434-3)

Baud rate	Min.	Max.
300 Baud	36,7ms	1150ms

2400 Baud	4,6ms	187,5ms

4800 Baud	2,3ms	118,8ms

9600 Baud	1,2ms	84,4ms

In this section the data link layer is described. One of the frames used in the M-Bus standard is shown below. The other M-Bus frames can be found in section 4.1.

The function field specifies the direction of the data flow and has various additional tasks in both calling and replying directions but many of these are optional and therefore not implemented.

Bit Number	7	6	5	4	3	2	1	0

Calling	0	1	FCB	FCV	F3	F2	F1	F0
direction

Reply	0	0	ACD	DFC	F3	F2	F1	F0
Direction

•Bit7 reserved for future use.

•Bit6 specifies the direction of the data flow. If it is set to 1 the communication has the direction Master to slave and vice versa if it is set to 0.

•FCB The slave do not act on this bit and is always sending new data.

•FCV The slave ignores this bit.

•DFC (data flow control) Not supported must be 0.

•ACD (Access demand) Not supported must be 0.

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•Control field F3-F0 the control field code tells the function or action of the message. The control field has 7 predefined control field shown below.

Name	C field binary	C field	Telegram	Description
		(HEX)

SND_NKE	0100 0000	40	Short frame	Initialization of slave

SND_UD	01F1 0011	53/73	Long/Control	Send user data to slave

REQ_UD1	01F1 1010	5A/7A	Short frame	Request class 1 data

REQ_UD2	01F1 1011	5B/7B	Short frame	Request class 2 data

REQ_SKE	0100 1001	49	Short frame	Status request

RSP_SKE	0000 1011	0B	Short frame	Status data, slave to
				master

RSP_UD	00AD 1000	08	Long/Control	Data transfer from slave
				to master after request

REQ_UD1 telegrams are answered with ACK because the Alarm protocols are not supported.

The primary address of the meter can be set to a value from 0-250. The default primary address is part of the serial number (red letters: ssssswwNNyyww) and is always a number from 00-99. To change the primary address either use the SonoApp or M-Bus command described later in this document.

Point-to-point addressing (0xFE) is intended for communication using the infrared eye or for network with only one slave (used for test of network with one slave).

Broadcast (0xFF) is used to communicate across the network to all the slaves e.g. to set a new baud rate on all slaves at the same time. Be aware that no acknowledge byte is replied from the slave in broadcast mode.

The secondary address can be used to select a slave. This slave can then afterwards be contacted using the primary address FDH. All slaves have an unique secondary address which ensures only a single slave answers.

Addressing Form	Slave Addressing
Primary addressing	0-250

Secondary	253 (FDH)
addressing and
selected slave

Point-to-Point	254 (FEH)
addressing

Broadcast	255 (FFH)

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The Length Field (L Field) defines the number of bytes (expressed in hex value) of the Active Data making up the telegram, plus 3 bytes for the C, A and Cl Fields.

This field is always transmitted twice in Long Telegrams (RSP_UD) see 4.1.

The Checksum (CS Field) serves to recognize transmission and synchronization faults. The checksum is calculated on the Active Data making up the telegram, plus 3 bytes for the C, A and Cl Fields. All bytes are added together in a 8 bit unsigned integer, which means that when the value gets larger than FFh it will wrap around and start all over.

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The CI-Field declares the transportation direction and the Application protocol (if exists). The CI-Field declares also which type of Transport Layer (“None”, “Short” and “Long” header) is applied.

In the SonoSelect/Safe meters with wired M-Bust the long header (0x72) is always used.

The SonoSelect/Safe meters supports the following CI-Fields.

CI-field (HEX)	Direction

50	Application reset

51	Data send to device

52	Slave select (no header)

72	The telegram contains data for the master
	with long header

B8	Set baud rate 300 (only wired M-Bus)

BB	Set Baud Rate to 2400

BD	Set Baud Rate to 9600

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The long header contains 12 bytes which is used to identify the Meter, hold track of new or old message and to apply encryption.

The encryption is not currently available for wired Danfoss Meters which means the configuration field always is 0000H.

The 12 byte long header is shown in the table below:

Byte Nr.	Size(Byte)	Value(Hex)	Description
1-4	4	xx xx xx xx	Meter identification number

5-6	2	D310	Manufacturer’s ID (DFS Danfoss 10D3h)

7	1	xx	Version number firmware (00-FF)

8	1	04/0C	Medium: Heat outlet/inlet

9	1	xx	Access Number (00-FF-> 00)

10	1	xx	Status

11-12	2	0000	Configuration

The identification number (secondary address) is a non-changeable (according to OMS) number in between 00000000 and 99999999. The identification number is part of the Danfoss Meters serial number and is unique. (In installations with other meters where same address is present the address can be change with SonoApp or M-Bus command shown later)

The secondary address is derived from the serial number. The serial number has the following format:

ssssswwNNyyww

The secondary address has the following format

ywwsssss

The manufactures ID is used to identify the manufacture of the Meter. Each manufacture has a flag consisting of three capital letters which can be combined to two bytes according to EN13757-3. The Danfoss manufacture flag is DFS (10D3h) and this flag is always part of the long header.

The version number is used to identify if the meter is of type:

•SonoSafe (0x01)

•SonoSelect (0x02).

The medium byte identifies the flow sensor installation of the Meter and has two settings for each meter type:

•Heat Inlet meters (supply 0x0C)

•Heat Outlet meters (return 0x04).

•Cooling Meter (Volume measured at return temperature: outlet)

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•Cooling Meter (Volume measured at flow temperature: inlet)

•Combined meter

•Water meter (For pulse readout only)

The Access Number has an unsigned binary coding and is incremented (modulo 256) by one after each RSP-UD is send from the slave.

The status byte is used to indicate different potential errors in the Meter. The errors are stated in the table below:

Bit	Meaning with bit set	Significance with bit not set
0,1	See table 5	See table 5

2	Power Low	Power Ok

3	Permanent error	No Permanent error

4	Temporary error	No Temporary error

5	Specific to manufacturer	Specific to manufacturer

6	Specific to manufacturer	Specific to manufacturer

7	Specific to manufacturer	Specific to manufacturer


	Status bit 1 bit 0

	0 0	No Error

	0 1	Application busy

	1 0	Any application error

	1 1	Abnormal condition/alarm

The status bit shall be used in this meaning:

Power low:

Warning – The bit “Power Low” is set only to signal interruption of external power supply or end of battery life time

Permanent error:

Failure – The bit “Permanent error” is set only if the meter signals a fatal device error which requires a service action.

Temporary error:

Warning – The bit “Temporary error” is set only if the meter signals a slight error condition which not immediately requires a service action. This could be an error which may later disappear.

Any application error:

The application error shall be used to communicate a failure during the interpretation or execution of a received command, e.g. a message which could not be decrypted.

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Abnormal conditions:

Shall be used if a correct working application detects an abnormal behavior like a permanent high flow.

The most critical active E-number (Error shown in the display) is sent as the status byte. The most critical error is E1 and least critical is E32.

Below is a table showing the bit pattern.

E-

E10

E11

E12

E13

Number

Hex

0x08

0x10

0x28

0x04

0x24

0x30

0x50

0x70

0x90

0xB0

0xD0

0xF0

0x48

code

E-

E14

E15

E16

E17

E18

E32

Number

Hex

0x40

0x44

0x60

0x62

0x13

0x92

code

Error type

E number

Power Low

E4, E5, E15

Permanent error

E1, E3, E13

Temporary error

E2, E6, E7, E8, E9, E10, E11, E12, E14, E16,

E17, E18, E32

The application layer contains the data sent from the slave to the master or vice versa.

Every data record sent which is not manufacture specific have the following data record header (DRH)

Data Information Block (DIB)		Value Information Block (VIB)
DIF	DIFE	VIF	VIFE	Data

1 Byte	0-10Byte(s)	1 Bytes	0-10 Byte(s)	0-n Bytes

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The Data Information Block (DIB) contains at least one DIF but can be extended by 10 DIFE if needed.

The DIFs supported by the Danfoss Meters:

Bit	Name		Description
7	Extension Bit	Specifies if a DIFE byte follows:
		0 = No
		1 = Yes

6	LSB of Storage Number	0 if log is not send

5-4	Function Field	Specifies the kind of value
		00 = instantaneous value
		01 = Maximum value
		10 = Minimum Value
		11 = Value during error state

3-0	Data Field	Length and Coding of Data:
		0001	(0x01): 8 Bit Integer
		0010	(0x02): 16 Bit Integer
		0011	(0x03): 24 Bit Integer
		0100	(0x04): 32 Bit Integer
		0110	(0x06): 48 bit Integer (only for record)
		0111	(0x07): 64 Bit Integer (only for record)
		1001	(0x09): 2 digit BCD
		1010	(0x0A): 4 digit BCD
		1011	(0x0B) 6 digit BCD
		1100	(0x0C): 8 digit BCD
		1101	(0x0D): Variable length (Only for TX)
		1111	(0x0F): Manufacture Specific Data

The DIFE supported by Danfoss Meters:

Bit	Name		Description
7	Extension Bit	Specifies if a DIFE byte follows:
		0	= No
		1	= Yes

6	Unit	Specifies if it is pulse counter or cooling value

5-4	Tariff	Used oC*m^3 records
3-0	Storage number	0000 (only used for logs)

The DIFE is used for selection of pulse 1 and pulse 2 counters. If first DIFE has the unit set to 1, it is pulse counter 1 and if the unit is set in the second DIFE, it is pulse counter 2 (see 4.4.2.7). The DIFE unit 3 is used for cooling records (Energy, Volume, Max Flow, Max Power).

The DIFE storage number is used to show the log values and which type of log there are sent.

The storage number 1 & 2 are used for year log 1 and 2.

The storage number from 3-26 is used for month log 1-24.

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