Siemens MOBY FC 56 Technical Description page 132

Programming MOBY-ASM on PROFIBUS-DP-V1
B.4 Blocking of Long Data Sequences
Since it is not possible to work with telegrams of indefinite length, the telegram is
formed into blocks, i.e. telegrams are transmitted in segments.
Blocking can be used with READ, WRITE, UPDATE, QUEUE-WRITE,
QUEUE-READ, LOAD, MOVE, DIR and TRACE commands. Blocking is controlled
by the parameters ADB (no. of data blocks) and DBN (current data block no.) in
the telegram heading.
The file description immediately follows the DBL parameter in the first command
telegram to the filehandler (DBN = 1). It contains the file name, start address and
length of the file. The file description is omitted from subsequent telegram
segments (DBN > 1).
The maximum block length (maximum length of a telegram segment) can be set
using the RESET command. The default block length is 128. The maximum block
length which can be set is 239.
The blocking sequence can be aborted using the RESET command. The blocking
sequence will be ended. No further acknowledgement of the aborted command will
be issued.
All other commands within a blocking sequence will be rejected by the ASM with
an error message. The present status of the blocking sequence remains
unchanged.
B-10
FC 56
J31069-D0155-U001-A0-7618