Siemens Automation System S7-400 - Manual (Page 221)

Glossary
Glossary-13
Automation System S7-400 Hardware and Installation
A5E00850741-01
Segment
→ Bus segment
SFB
→ System Function Block
SFC
→ System Function
Signal Module
Signal modules (SMs) are the interface between the process and the
programmable controller. Signal modules comprise digital input and output
modules (I/O module, digital) and analog input and output modules (I/O module,
analog).
Slave
A slave may only exchange data when requested by a master.
STARTUP
The CPU goes through the STARTUP state during the transition from STOP to
RUN mode. It can be set using the mode selector on the CPU, following power-on,
or by an operation on the programming device.
Status interrupt
Can be generated by a DPV1 slave. The DPV1 master responds with a call of
OB55.
For detailed information on OB57, refer to the “System Software for
S7-300/S7-400 System and Standard Functions” reference manual.
STEP 7
Programming language for writing user programs for SIMATIC S7 programmable
controllers.
Substitute Value
Substitute values are values which are output to the process in the case of faulty
signal output modules or which are used in the user program instead of a process
variable in the case of faulty signal input modules. The substitute values can be
specified in advance by the user (for example, maintain old value).