Technical data

System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
19-1
19 SFCs for Global Data Communication
19.1 Sending a GD Packet with SFC 60 "GD_SND"
Description
With SFC 60 "GD_SND" (global data send), the data of a GD packet are collected
and then sent on the path specified in the GD packet. The GD packet must already
have been configured with STEP 7.
SFC 60 "GD_SND" can be called at any point in the user program.
The scan rate and the collection and sending of the data by the system at the cycle
checkpoint are not influenced by SFC 60 calls.
Interrupt ability
SFC 60 "GD_SND" can be interrupted by higher priority classes. It is also possible
that SFC 60 is called again for the same GD packet in the higher priority class.
The data are then collected and sent in the higher priority class. When the program
returns to the interrupted SFC, this is terminated immediately and the data that
have already been collected are discarded.
This procedure means that during the processing of the highest priority class,
consistent data are transferred (consistency in the sense defined for global data).
Data Consistency with GD
The following rules apply to the consistency of the data collected from the various
memory areas and sent.
The following are consistent:
• The simple data types (bit, byte, word, and double word)
• An array of the data types byte, word, and double word up to a maximum length
depending on the specific CPU.