Annex
9
gas-net
C1 and C2
Page 9-1
9 Annex
9.1 Host
protocols
9.1.1 RK512 / 3964R
The
gas-net
DSfG gateway supports the protocol consisting of 3964R (data link
layer) and RK512 (data presentation).
Look up the settings of the protocol parameters in exactly this form in the manu-
als of the programmable controller, and adjust them in the communications
processor procedure.
The implementation of the RK512 protocol in the
gas-net
Gateway is restricted
to the data transmission between data blocks. The smallest information unit is a
so-called
data word
. Such a data word has a length of 16 bits and may contain,
for instance, several messages, a status overview in the form of a bit string, or a
binary measurement.
The structure of the management of these data words is rather simple; there are
up to 256 larger units,
data blocks
, each of which may contain up to 256 data
words. Data blocks and words are numbered consecutively from 0 to 255, with
the numbers serving as addresses.
A single data word is clearly defined by exactly three details:
•
the address of the data block (0..255)
•
the address of the data word (0..255)
•
the content of the data word
The addresses to be assigned to the host data in the gateway parameterisation
therefore consist of a data block/data word (DB/DW) pair. The data block 0 is
usually used for intrasystem host variables. This is why you should use the data
block 0 neither for exporting values towards the host nor for importing host
values.
In some special cases the host only masters the subordinate 3964R protocol
layer.
This means that the following restriction applies: As no DB/DW information is
transmitted on the 3964R protocol level, all data to be exported or imported
must be arranged in a row. The number of data is thus limited to 64 data words
per transmission.
