Technical data

SFCs for Global Data Communication
System Software for S7-300/400 System and Standard Functions - Volume 2/2
19-4 A5E00739858-01
19.2 Programmed Acceptance of a Received GD Packet
with SFC 61 "GD_RCV"
Description
With SFC 61 "GD_RCV" (global data receive), the data from an incoming GD
frame for exactly one GD packet are retrieved and entered in the received GD
packet. This must already have been configured with STEP 7.
SFC 61 "GD_SND" can be called at any point in the user program.
The scan rate and the retrieving of the data by the system at the cycle checkpoint
are not influenced by SFC 61 calls.
Interrupt ability
SFC 61 can be interrupted by higher priority classes, however, only so that the
data consistency defined for global data remains guaranteed. If the processing of
the function is interrupted, it is possible that SFC 61 is called again for the same
GD packet in the higher priority class.
The data are then entered in the receive GD packet in the higher priority class.
When the program returns to the interrupted SFC, this is terminated immediately.
Data Consistency with GD
The following rules apply to the consistency of the data entered in the various
memory areas.
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
specific to the receiving CPU.