SSW7-RK512/RS422 5
Transmission
The SSW7-RK512/RS422 converts the RK512 protocol to the MPI bus. the RK 512
protocol transmits data with the 3964/R procedure. The BCC of the 3964/R
procedure is always activated in the SSW7-RK512/RS422. The transmission format is
predefined as 8 data bits, even parity, and 1 stop bit.
Data words, flags, input and output bytes can be transmitted. In general, only fetch
and send requests from the serial partner are supported. The programmable
controller cannot access the SSW7-RK512/RS422 or the communication partner
behind it on its own initiative.
As the RK512 protocol only supports word-oriented addressing of data words, the
word address is converted to a corresponding byte address. If DW10 is specified as
the source or destination address, the SSW7-RK512/RS422 requests DBW20 (DBB20
& DBB21) from the CPU. In the case of inputs, outputs, and flags, however, both the
RK512 and the MPI bus are byte oriented, i.e. there is no conversion.
The SSW7-RK512/RS422 supports continuation frames for which the standard block
size is 128 bytes. The highest addressable byte address is 255 and the highest word
address is 254.
The SSW7-RK512/RS422 is set to address 5 in the factory and establishes a
connection with address 2. The destination address and the local address can be set
in DB0. The SSW7-RK512/RS422 first signs on to the bus and then establishes a
connection with the destination CPU if a valid RK512 frame has been received from
the serial partner.
A description of the RK512 protocol is available on request.
Extended protocol
In addition to the standard RK512 protocol, the SSW7-RK512/RS422 also contains a
proprietary protocol extension for addressing all memory areas of S7 controllers.
Before the protocol extension can be used, the protocol driver on the PC or operator
terminal must be adapted by the manufacturer. A description of the extended RK512
protocol is available on request.
