
Communication Services
4-12
SIMATIC 505 PROFIBUS-FMS CP User Manual
4.5 Peerlink II Services
Peerlink
II is an unacknowledged broadcast service that allows the FMS CP
module to transmit one peer block to other stations and receive up to 31
peer blocks from other FMS CP modules on a scan-by-scan (cyclic) basis, as
shown in Figure 4-7.
Transmit
Note:
Transmit is an unacknowledged broadcast.
SIMA
TIC 505
FMS CP
CPU
505 Network
Data from memory
Transmit
One
block of data stored in
a specified memory address
in the local station is
transmitted to the network.
The block is configured by a
name, a descriptor ID, and
an address.
Data Flow
TRANSMIT
Receive
Note:
Data is received when it becomes available on the network.
SIMA
TIC 505
FMS CP
CPU
505 Network
Receive
Up
to 31 blocks of data can
be received from the network
by the local station and are
stored in a specified memory
address. The local station
picks these blocks from the
network based on their
descriptor ID.
Data Flow
RECEIVE
Figure 4-7 Peerlink
II Services Data Flow
Y
ou configure the interval between transmissions of the data as a number of
programmable logic controller scans (see Section 5.5). If the FMS CP module
is unable to transmit at the rate selected, it transmits as often as possible.
Received data is stored by the FMS CP module. If the FMS CP module is
unable to process received data at the rate at which it is received, it stores
the most recently processed data.
NOTE:
No status information is stored by Peerlink II services. If the
FMS CP module is unable to process data at the requested transmission
interval rate, the FMS CP module does not generate an error message in
the status report. (Refer to Chapter 7 for information on viewing actual peer
transmit intervals in the Peer Block Status diagnostics dialog.)
T
ransmitting and
Receiving
Peer Blocks
Transmission
Intervals
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