Siemens Simatic S7-400 - Manual (Page 611)

Glossary
Glossary-5
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Direct communication
Direct communication involves assigning local input address areas of an
intelligent DP slave (for example, CPU 315-2 with PROFIBUS DP connection) or
of a DP master to the input address areas of a PROFIBUS DP partner. The
intelligent DP slave or DP master receives the input data that the PROFIBUS DP
partner sends to its DP master via these assigned input address areas.
DP master
A node with a master function in the PROFIBUS DP. A master that behaves in
accordance with the EN 50170 with the DP protocol is a DP master. The bus
access right (token) is only passed amongst masters. The slaves, in this case DP
slaves, can only respond on the request of a master. The following distinctions
are made:
DP master (class 1): executes the user data communication with the DP slaves
assigned to it.
DP master (class 2): provides services such as: reading of the input/output data,
diagnostics, global control.
DP slave
A ³ slave that is operated on the PROFIBUS bus system with the
PROFIBUS DP protocol is called a DP slave.
Edge, falling
Signal status change from 1 to 0
Edge, rising
Signal status change from 0 to 1
EEPROM
Electrically erasable programmable read-only memory
EPROM
Erasable programmable read-only memory
Equidistance
Equidistance is a DP bus cycle that is accurate to a few
m
s and can be configured
in STEP 7.