Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 221)

Glossary
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
Glossary-5
Diagnostic buffer
The diagnostics buffer represents a buffered memory area in the CPU. It stores diagnostic
events in the order of their occurrence.
Diagnostic Interrupt
Modules capable of diagnostics operations report detected system errors to the CPU by
means of diagnostic interrupts.
Diagnostics
See System diagnostics
DP master
A master which behaves in accordance with EN 50170, Part 3 is known as a DP master.
DP slave
A slave operated on PROFIBUS with PROFIBUS DP protocol and in accordance with EN
50170, Part 3 is referred to as DP slave.
DPV1
The designation DPV1 means extension of the functionality of the acyclical services (to
include new interrupts, for example) provided by the DP protocol. The DPV1 functionality has
been incorporated into IEC 61158/EN 50170, volume 2, PROFIBUS.
Electrically isolated
The reference potential of the control and on-load power circuits of isolated I/O modules is
electrically isolated; for example, by optocouplers, relay contact or transformer. I/O circuits
can be interconnected with a root circuit.
Equipotential bonding
Electrical connection (equipotential bonding conductor) which eliminates potential difference
between electrical equipment and external conductive bodies by drawing potential to the
same or near the same level, in order to prevent disturbing or dangerous voltages between
these bodies.
Error display
One of the possible reactions of the operating system to a runtime error is to output an error
message. Further reactions: Error reaction in the user program, CPU in STOP.
Error handling via OB
After the operating system has detected a specific error (e.g. access error with STEP 7), it
calls a dedicated block (Error OB) that determines further CPU actions.