Technical data

Table Of Contents
Generating Block-Related Messages
System Software for S7-300/400 System and Standard Functions - Volume 2/2
24-28
A5E00739858-01
Amount of transferable data
The amount of data transferable using the accompanying value SD for SFCs
ALARM_S, ALARM_SQ, ALARM_D and ALARM_DQ cannot exceed a maximum
length. This data length is calculated as follows:
maxleng = min (pdu_local, pdu_remote) - 48
Definitions:
pdu_local: the maximum length for CPU data blocks (SZL_ID W#16#0131,
INDEX 1, Variable pdu)
pdu_remote: the maximum length for display device data blocks
Example:
A CPU 414-1 sends a message to a programming device PG 760 (via MPI).
pdu_local = 480 Byte, pdu_remote = 480 bytes,
Result:
maxleng = min (480, 480) - 48 = 480 - 48 = 432
The maximum transferable data length per SFC is thus 432 bytes.