Isochrone Updating Of The Process Image Partition - Siemens SIMATIC S7-400 Reference Manual

Structure of a CPU 41x
1.11.3

Isochrone Updating of the Process Image Partition

With SFC 126 "SYNC_PI" you can update a process image partition of the inputs
synchronous to the clock. A user program linked to a DP cycle can use this SFC to
consistently and synchronously update input data located in a process image
partition. SFC 126 can be interrupted and can only be called in OBs 61, 62, 63 and
64.
With SFC 127 "SYNC_PO" you can update a process image partition of the
outputs synchronous to the clock. A user program linked to a DP cycle can use this
SFC to synchronously update output data located in a process image partition and
consistently transmit them to I/O devices. SFC 127 can be interrupted and can
only be called in OBs 61, 62, 63 and 64.
To be able to update process image partitions synchronous to the clock, all input or
output addresses of a slaves must be assigned to the same process image
partition.
To ensure the consistency in a process image partition during each cycle, the
following requirements must be fulfilled for each CPUs:
• CPU 412:
• CPU 414:
• CPU 416:
• CPU 417:
SFC 126 and 127 are documented in the corresponding online help and in the
manual "System and Standard Functions".
1-40
number of slaves + number of bytes / 100 < 10
number of slaves + number of bytes / 50 < 20
number of slaves + number of bytes / 50 < 26
number of slaves + number of bytes / 50 < 20
Automation System S7-400 CPU Specifications
A5E00165965-01