ProSoft Technology PTQ-PDPMV1 - Manual (Page 210)

Hot Standby Support PTQ-PDPMV1 ♦ Quantum Platform
User Manual PROFIBUS DP Master Network Interface Module for Quantum
Page 210 of 306 ProSoft Technology, Inc.
August 12, 2014
Slave Status Example
M
A
M
P
Type of Failure Local "SO-bit" HSBY Nr of local
slaves
Local "SO-bit" HSBY Nr of local
slaves
No errors 1 3 1 3
Cable is cut at 1. 0 0 1 3
Cable is cut at 2. 0 1 0 2
Cable is cut at 3. 0 2 0 1
Cable is cut at 4 1 3 0 0
S1 is disconnected 0 2 0 2
Database Mismatch
Both Masters inform the counterpart of its database CRC value as a part of the
Crossed Status Information.
Based on this information, both Masters compare their own CRC values with the
one received from the counterpart to determine the state of the "DB-bit" in the
"HSBY Local status" register.
It does not make sense to perform the CRC check in a cyclic manner. Instead, it
would be enough to do it once when the counterpart has just been detected.
FDL Layer Access
Ping messages, slave status messages, and DPV1 status messages are
communicated over the PROFIBUS network via the FDL-layer of the Siemens
stack (a.k.a. AMPRO2).
A unique channel, reserved only for ping and slave status messages, is opened
to the FDL-layer.
This would ensure that no "DPV1 class 2"- or "Live List" requests, which also use
the FDL-layer, are interfering with the time-critical ping or slave status sequence.
Message type and priority
 Ping messages are sent as high-priority SRD-repeat telegrams
 Slave status messages are sent as low-priority FDL_Status-repeat telegrams
 DPV1 status messages are sent as low-priority SRD (single) telegrams