Operation

When the product does not have any contact with the ABB electricity meter, the LED will turn red and no data is sent. As long as the CMeX20w is powered, it will keep searching for an ABB electricity meter to connect to.

In normal operation unencrypted mode, the product will send unencrypted messages every 16th seconds. This mode is normally used when the master or AMR/AMM system does not handle AES encryption or if the AES key is unknown to the system.

In unencrypted mode, the information is sent in a wireless telegram with "short application header" (Cl= 0x7A). The unencrypted telegram contains only one address, "link layer address", which is composed of data that is taken from the header in the ABB electricity meter's telegram ("Manufacturer code, ID, Version and Device type). ln unencrypted mode, the CMeX20w is not sending its own address in the telegram.

In normal operation encrypted mode, the product will send encrypted messages every 16th seconds. This mode is used to secure data that is sent from the product to the master or AMR/AMM system. To decrypt data, the master or system must know the unique 128 bit AES key to the meter. The unique 128 bit AES key is given at the delivery or at the demand of the customer.

In encrypted mode, the information is sent in a wireless telegram with "long application header" (Cl= 0x72). The encrypted telegram contains two addresses, the CMeX20w's own address that is needed for choosing the right key for decryption and the ABB meter's address "Application layer address", which is included in "long application header" and contains data taken from the header in the ABB meter's telegram ("Manufacturer code, ID, Version and Device type). The telegram's "link layer address" contains the CMeX20w's own address ("Manucfacturer code, ID, Version and Device type). Device type for CMeX20w is 0x37 = "Radio converter, meter side".

In encrypted mode, a unique 128 bit AES key is required for all telegrams. It will be given either upon delivery or upon customer request.

At operation in encrypted mode, the product can be identified by the following information in the "Link Layer Address":

The product uses wireless M-Bus mode T1.

All bytes from index 0 (L-field) are 4-to-6-bit coded according to the standard for wireless M-Bus mode T1. CRC byte and 4/8-bit postamble are also sent according to the standard but are not shown in the following table.

Byte index 2..9 is "Link layer address" that contains the address of the meter. Byte index 11..14 is "short application header".

All bytes from index 0 (L-field) is 4-to-6-bit coded according to the standard for Wireless M­ Bus mode T1. CRC-byte and 4/8-bit postamble are also sent according to the standard but are not shown in the following table.

Byte index 2..9 is "Link layer address" that contains the address of CMeX20w. Byte index 11..22 is "long application header" where index 11..18 is "application layer address" here contains the meter's address.