Technical data

11.4 Basics of Data Transmission Using the DP Service
of the CP
This section describes the functions of the DP service from the point of view
of the CPU control program.
With data transmission using L2-DP, the data exchange is handled via the
I/O area of the SIMATIC PLC.
This means the following:
➣
The transmitted data are transferred to the CP by the control program
with STEP-5 commands directly or using the operating system function
PIQ (Output process image of the outputs).
➣
The received data are fetched from the CP by the control program with
STEP-5 commands directly or using the operating system function PII
(Update process image of the inputs).
All the I/O bytes you want to use for sending and for receiving must be
identified as DP I/Os when the I/O areas are configured in the COM.
Communication with distributed I/Os is only permitted using the base
interface number (base SSNR) .
☞
Simultaneous use of DP and GP is not possible
Distributed I/Os (DP) B89060/02
Volume 1 11 - 10