Administration

M-Bus product identification

The product can be identified using the following information:

Manufacturer string = ELV
Medium = Room sensor
Generation = 70-79

The Generation field between product releases will only change (increase by 1) if the M-Bus protocol information changes between versions. Use the software version field in the M-Bus telegram to identify current software version.

M-Bus addressing mode

The product implements both primary and secondary addressing mode. The primary and secondary addresses can be changed using M-Bus standard command. Primary address from factory is 0 and secondary address from factory is the fabrication number (serial number).

M-Bus baud rate

The product can handle 300 or 2400 baud. No auto-baud detection is available. The baud rate can be changed using M-Bus standard commands. Baud rate from factory is 2400 baud.

FCB-bit toggling (multi-telegram)

Multi-telegram mode, or FCB-bit toggling, is implemented. First telegram contains momentary values, min/max and average values of measured temperature and humidity. Second telegram contains last 24 hours of temperature values.

M-Bus break

M-Bus master break signals are handled according to the M-Bus standard. Any on-going communication from M-Bus slave to master will be aborted on break detection from the M-Bus master.

M-Bus commands

Initialize product (SND_NKE)

Table 127. Master to slave

Byte index	Data	Description
0	0x10	Start character
1	0x40	C-Field = SND_NKE
2	0xnn	A-Field = Address of slave
3	0xnn	Checksum
4	0x16	Stop character

Request user data (REQ_UD2)

Request user data from product and wait for slave response.

Table 129. Master to slave

Byte index	Data	Description
0	0x10	Start character
1	0x4b \| 0x5b \| 0x6b \| 0x7b	C-Field = REQ_UD2
2	0xnn	A-Field = Address of slave
3	0xnn	Checksum
4	0x16	Stop character

The RSP_UD telegram depends on the FCV and FCB bits in the C field of the calling REQ_UD2 telegram. There are two telegrams available:

If FCV is 0 in REQ_UD2 or if first, third, fifth etc. REQ_UD2 since last SND_NKE (primary addressing mode) or if first, third, fifth etc. REQ_UD2 since last successful secondary addressing selection first telegram is returned.
If FCV is 1 in REQ_UD2 and if second, fourth, sixth etc. REQ_UD2 since last SND_NKE (primary addressing mode) or if second, fourth, sixth etc. REQ_UD2 since last successful secondary addressing selection second telegram is returned.

Table 130. Slave to master – Telegram 1

Byte index	Data	Description
0	0x68	Start character 1
1	0xnn	L-field 1
2	0xnn	L-field 2
3	0x68	Start character 2
4	0x08	RSP-UD
5	0xnn	A-field = Primary address
6	0x72	Variable data respond, mode 1 = LSByte first
7-10	0xnnnnnnnn	Secondary address
11-12	0x9615	Manufacturer id “ELV”
13	0xnn	Generation field In the range from 70 to 79 (dec)
14	0x1B	Device type/medium = room sensor
15	0xnn	Access number
16	0x00	Status byte 0x00 = Ok (no error) 0x0a = Sensor failure (permanent application error)
17-18	0x0000	Signature, 16 bit binary
19	0x01	Product status DIF
20	0xfd	Product status VIF
21	0x1b	Product status VIFE = digital input
22	0xnn	8-bit integer value with following bit-mask: Bit 7: Not used (= 0 or 1) Bit 6: Not used (= 0 or 1) Bit 5, 4, 3: Not used (= 0) Bit 2: 24 h average value indicator Toggles when the 24 h average temperature is updated (every hour) Bit 1: 1 h average value indicator Toggles when the 1 h average is updated (every 6 minute) Bit 0: Sensor failure 1 = Sensor failure (same as 0x0a in header status byte) 0 = No sensor failure
23	0x02	Instantaneous relative humidity DIF
24	0xfb	Instantaneous relative humidity VIF
25	0x9b	Relative humidity, in % (integer) VIFE
26	0x74	Scaling VIFE, x 0.01
27..28	0xnnnn	Instantaneous relative humidity In case of error the relative humidity will be set to 0. An optional humidity VIF can be selected in the setup menu. In this case the 3 byte default VIF is replaced by 0xFC0348522574
29	0x22	Minimum relative humidity DIF
30	0xfb	Minimum relative humidity VIF
31	0x9b	Minimum Relative humidity, in % (integer) VIFE
32	0x74	Scaling VIFE, x 0.01
33..34	0xnnnn	Minimum Instantaneous relative humidity In case of error the minimum relative humidity will be set to 0. This is the lowest instantaneous relative humidity since last min/max reset command. An optional humidity VIF can be selected in the setup menu. In this case the 3 byte default VIF is replaced by 0xFC0348522574
35	0x12	Maximum relative humidity DIF
36	0xfb	Maximum relative humidity VIF
37	0x9b	Maximum Relative humidity, in % (integer) VIFE
38	0x74	Scaling VIFE, x 0.01
39..40	0xnnnn	Maximum Instantaneous relative humidity In case of error the maximum relative humidity will be set to 0. This is the highest instantaneous relative humidity since last min/max reset command. An optional humidity VIF can be selected in the setup menu. In this case the 3 byte default VIF is replaced by 0xFC0348522574
41	0x02	Instantaneous temperature DIF
42	0x65	Instantaneous temperature VIF, external temperature
43..44	0xnnnn	Instantaneous temperature x 100 In case of error the temperature will be set to 0.
45	0x22	Minimum temperature DIF
46	0x65	Minimum temperature VIF, external temperature
47..48	0xnnnn	Minimum temperature x 100 In case of error the temperature will be set to 0. This is the lowest instantaneous temperature since last min/max reset command.
49	0x12	Maximum temperature DIF
50	0x65	Maximum temperature VIF, external
51..52	0xnnnn	Maximum temperature x 100 In case of error the temperature will be set to 0. This is the highest instantaneous temperature since last min/max reset command.
53	0x01	Average duration DIF
54	0x72	Average duration VIF
55	0xnn	Number of hour averages collected since power-on (0..24) This counter starts from zero at power-on and is incremented once per hour when a new hour average temperature value is stored in the 24-hour table. The counter does not count beyond 24 (i.e. this value is equal to number of valid hour values stored in the 24-hour table). The 24-hour temperature rolling average will not be available until this counter has reached 24.
56	0x42 \| 0x72	1-hour temperature rolling average DIF, storage number 1 0x42 = The value is available 0x72 = The value is not yet calculated
57	0x65	1-hour temperature rolling average VIF, external temperature
58..59	0xnnnn	1-hour temperature rolling average x 100 This value is unavailable (0) until 1 hour has passed since power-on. During this first hour the value will be flagged as “value during error state”, DIF bits 5 and 4 = 1. This value is updated every 6 minute. The temperature data will be 0 in case of sensor error. See slave status byte in data header.
60	0x82 \| 0xb2	24-hour temperature rolling average DIF, storage number 2 0x82 = The value is available 0xb2 = The value is not yet calculated
61	0x01	24-hour temperature rolling average DIFE
62	0x65	24-hour temperature rolling average VIF, external temperature
63..64	0xnnnn	24-hour temperature rolling average x 100 This value is unavailable (0) until 24 hour has passed since power-on. During this period the value will be flagged as “value during error state”, DIF bits 5 and 4 = 1. This value is updated every hour. The temperature data will be 0 in case of sensor error. See slave status byte in data header.
65	0x0c	Fabrication number DIF
66	0x78	Fabrication number VIF
67..68	0xnnnnnnnn	Fabrication number, 8-digit packed BCD
69	0x0d	Firmware version DIF
70	0xfd	Firmware version VIF
71	0x0f	Firmware version VIFE = “ Other software version”
72	0x05	Length of firmware string (varying)
73..77	0xnnnnnnnnnn	Firmware version string in format: Major.Minor.PatchLevel
78	0x1f	End of telegram, more data follows
79	0xnn	Checksum
80	0x16	Stop character

Table 131. Slave to master – Telegram 2

Byte index	Data	Description
0	0x68	Start character 1
1	0xnn	L-Field 1
2	0xnn	L-Field 2
3	0x68	Start character 2
4	0x08	RSP_UD
5	0xnn	A-Field = Primary address
6	0x72	Variable data respond, mode 1 = LSByte first
7-10	0xnnnnnnnn	Secondary address
11-12	0x9615	Manufacturer id “ELV”
13	0xnn	Generation field In the range from 70 to 79 (dec)
14	0x1B	Device type/medium = room sensor
15	0xnn	Access number
16	0xnn	Status byte 0x00 = Ok (no error) 0x0a = Sensor failure (permanent application error)
17-18	0x0000	Signature, 16 bit binary
19 + 5 x N	0xc2 \| 0xf2 \| 0x82 \| 0xb2	24-hour log temperature table DIF Table index = N = 0..23 Storage numbers N + 3 = 3..26 Value age = N (+1/-0) hours The newest value is transmitted first. During the first 24 hours after power-on, values are sent as 0 and flagged as “value during error state” (DIF bits 5 and 4 = 1), while not yet updated. All temperature data will be 0 in case of sensor error. See product status byte or status byte in data header.
19 + 5 x N	0xnn	24-hour log temperature table DIFE nn = (N+3/2)
20 + 5 x N	0x65	24-hour log temperature table VIFE
21..22 + 5 x N	0xnnnn	Average temperature of hour “now – N” x 100
23 + 5 x N	0x0f	End of telegram, no more data follows
23 + 5 x N +1	0xnn	Checksum
23 + 5 x N +2	0x16	Stop character

Set baud rate

Set baud rate of slave.

Table 132. Master to slave

Byte index	Data	Description
0	0x68	Start character 1
1	0x03	L-field 1
2	0x03	L-field 2
3	0x68	Start character 2
4	0x43 \| 0x53 \| 0x63 \| 0x73	C-Field = SND-UD
5	0xnn	A-Field = Primary address
6	0xnn	CI-Field = Baud rate selection code: 0xb8 = 300 baud 0xb9 = 600 baud 0xbA = 1200 baud 0xbb = 2400 baud 0xbc = 4800 baud (note 1) 0xbd = 9600 baud (note 1) 0xbe = no change (note 2) 0xbf = no change (note 2) Baud rates > 2400 baud do work but have not been tested to comply with the timing specifications in the M-Bus standard. Baud rate codes 0xbe and 0xbf are ACKed with 0xe5 although they do not change the baud rate (this is in accordance with the M-Bus specification).
7	0xnn	Checksum
8	0x16	Stop character

Application reset

Restore all information to factory default.

Table 134. Master to slave

Byte index	Data	Description
0	0x68	Start character 1
1	0x04	L-field 1
2	0x04	L-field 2
3	0x68	Start character 2
4	0x43 \| 0x53 \| 0x63 \| 0x73	C-Field = SND-UD
5	0xnn	A-Field = Primary address
6	0x50	CI-Field = Application reset
7	0xb0	Application reset sub-code
8	0xnn	Checksum
9	0x16	Stop character

Set primary address

Change M-Bus primary address.

Table 136. Master to slave

Byte index	Data	Description
0	0x68	Start character 1
1	0x06	L-field 1
2	0x06	L-field 2
3	0x68	Start character 2
4	0x43 \| 0x53 \| 0x63 \| 0x73	C-Field = SND-UD
5	0xnn	A-Field = Primary address
6	0x51	CI-Field
7	0x01	Primary address DIF
8	0x7A	Primary address VIF
9	0xnn	New primary address (0x00-0xfa)
10	0xnn	Checksum
11	0x16	Stop character

Set secondary address

Change M-Bus secondary address.

Table 138. Master to slave

Byte index	Data	Description
0	0x68	Start character 1
1	0x09	L-Field 1
2	0x09	L-Field 2
3	0x68	Start character 2
4	0x43 \| 0x53 \| 0x63 \| 0x73	C-Field = SND-UD
5	0xnn	A-Field = Primary address
6	0x51	CI-Field
7	0x0c	Secondary address DIF
8	0x79	Secondary address VIF
9-12	0xnnnnnnnn	New secondary address, 8-bit packed BCD
13	0xnn	Checksum
14	0x16	Stop character

Select slave

Select slave for further secondary addressing. After successful selection, the slave can be addressed using primary address 253.

Table 140. Master to slave

Byte index	Data	Description
0	0x68	Start character 1
1	0xnn	L-field 1 Variable depending on selection mask. The selection mask can have any size in the range 0..8 bytes except 5 (manufacturer id requires a full 16-bit mask).
2	0xnn	L-field 2 Variable depending on selection mask.
3	0x68	Start character 2
4	0x43 \| 0x53 \| 0x63 \| 0x73	C-field = SND-UD
5	0xnn	A-Field = Primary address
6	0x52	CI-Field = Slave selection The slave will be deselected if there is any mismatch.
7-10	0xnnnnnnnn	Optional M-Bus secondary address mask, packed BCD The M-Bus ID mask can use the nibble 0xf as a wildcard in any of the eight BCD digit positions.
11-12	0xnnnn	Optional M-Bus manufacturer id mask, 16-bit binary The M-Bus manufacturer id mask can use 0xff as wildcard for one or both bytes.
13	0xnn	Optional M-Bus generation mask, 8-bit binary The M-Bus generation mask can use 0xff as wildcard.
14	0xnn	Optional M-Bus medium mask, 8-bit binary The M-Bus meter medium mask will match if 0x00 ("unknown") or 0xff (wildcard).
15	0xnn	Checksum
16	0x16	Stop character

Select humidity VIF code

This command will change the relative humidity VIF presentation.

This command was implemented in software version 4.1.0.

Table 142. Master to slave

Byte index	Data	Description
0	0x68	Start character 1
1	0x06	L-field 1
2	0x06	L-field 2
3	0x68	Start character 2
4	0x43 \| 0x53 \| 0x63 \| 0x73	C-field = SND-UD
5	0xnn	A-Field = Primary address
6	0x51	CI-field
7	0x0F	Manufacture specific follows DIF
8	0x06	Elvaco command select humidity VIF code
9	0xnn	Humidity VIF selector nn = Dimensionless (0xFDBA)=0x00 Plain text (%RH)=0x01
10	0xnn	Checksum
11	0x16	Stop character

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