BS/EN 13757-3-2018 pdf download.Communication systems for meters Part 3 : Application protocols.
NOTE I Structured manufacturer specific data (i.e. those with a known data structure including variable length binary or ASCII but with a manufacturer specific meaning or unit) can be described using normal data records with a value information field of VIF = or FFh (see 6.4.1).
The DIF = lFh signals additionally a request from the slave to the master to readout the slave once again. The master shall readout the slave until there is no DIF = lFh inside the responded datagram (multi datagram message readout) or use an application reset. The variable data block of the next datagram starts with a normal DIF. If a multi datagram message contains M-l3us records only and no manufacturer specific data, the DIF lFh shall be the last byte in the application frame of all except the last datagram.
DIF= lFh should be used for unencrypted data (security mode 0 in EN 13757-7:2018, Table 19). DIF= lFh shall not be used in combination with enabled fragmentation within AFL (see EN 13757-7, EN 13757-6). For encrypted multi datagram messages fragmentation in AFL should be applied instead oIDIF= lFh.
NOTE 2 If DIF = OFh Is used in combination with fragmentation in the AFL the manufacturer specific data are continued in the successive fragments (without repeated application of DIF = OFh at the beginning of the successive fragment).
In case of partial encryption (see EN 13757-7:2018, 7.6.5) DIF = OFh and the manufacturer specific data shall be located completely outside of the encrypted area.
If manufacturer specific data are to be transported in the encrypted part of a partially encrypted
message, a data record with a suitable DIF (possibly a DIF with variable length — see 6.3.3) and a
VIF = 7Fh or FFh (manufacturer specific data record — see 6.4.1) shall be used instead of the usual
MDH-DIF=OFh or lFh.
NOTE 3 A MDH hidden in the encrypted part of a partially encrypted message causes misinterpreting of following unencrypted data as long as encrypted data are not decrypted
7 Application reset and application select
7.1 ApplicatIon reset
With the Cl-field 50h or 53h (without additional parameter), the master can release a reset of the application layer In the slaves. Each slave itself decides which parameters to change. e.g. which data output is default — after it has received such an application reset.
7.2 Application select with subcode
It is allowed to use optional parameters after Cl = 50h or 53h’ In this case, the Cl-field acts as application select If more bytes follow, these bytes are the application select subcode. Up to 10 subcode bytes are possible. The application select subcode defines which message function and which block is requested by the master. The data type of this parameter is 8 bit binary. The upper 4 bits of each byte define the message application and the lower 4 bits of each byte define the number of the block or datagram number (the meaning of this number is device specific). The lower 4 bits may be ignored for slaves which provide only a single datagram for each application. The use of the value zero for the number of the block means that all datagrams are requested.
Message application and block number are calculated according to the following rules:
a) message from master to slave: Cl = 50h/53h ax by cz;
b) message from slave to master: Cl = 66h/67h/68h ax by cz;
c) using the bytes ax, by, cz as 8 bit binary:
1) message application: a (if a Fh);
2) message application: a + b (if a = Fh and b s
3) message application: a + b + c (if a = Fh, b = Fh and c ≤ Fh);
4) block number: x: Bit 0 to 3;
5) block number: y: Bit 4 to 7;
6) block number: z: Bit 8 to 11.BS/EN 13757-3-2018 pdf download.