User manual

PTQ-PDPMV1 ♦ Quantum Platform Hot Standby Support
PROFIBUS DP Master Network Interface Module for Quantum User Manual
ProSoft Technology, Inc. Page 219 of 306
August 12, 2014
The PROFIBUS DP transfer rate is fixed at 93.75 kbit/s for non-modular segment
couplers. The bit time is thus tbit DP = 10.67 µs. The PROFIBUS PA transfer rate
is fixed at 31.25 kBit/s; while the bit time is tbit PA = 32 µs.
The slot-time setting of the table above works if the total of input data bytes plus
output data bytes < 253 bytes. If the data volume of a PROFIBUS PA slave
exceeds this value, the slot-time should be set to 7192 [tbit DP]. For purposes of
optimization, the ideal setting can be calculated as follows:
TSL > 13*(LS + LR) + 3*TSDR + 630
where LS is the number of data bytes in the Master_Request telegram and LR is
the number of data bytes in the Slave_Response telegram.
Time TSDR refers to the actual time lapse that is counted between the
Master_Request and the Slave_Response. This is typically 75 tbit DP.
Other possibilities for optimization in terms of cycle times are available through
the Idle1-Time, Idle2-Time and the HSA setting.
The Idle1-Time (TID1) is an idle time to be observed by the Master between a
response telegram and the prompt telegram following it. The TID1 parameter
cannot be set directly in many tools. To optimize the Idle-Time in spite of this, the
Setup-Time TSET parameter or, if it cannot be adjusted either, the Quiet-Time
TQUI parameter must be adjusted. The Idle-Time is calculated as follows:
TID1 = 2*TSET + TQUI + 35*tbit DP
TID1 depends on the maximum response time (not to be confused with the
Station-Delay-Time TSDR) of all PA bus stations. In the table above, values are
indicated for TID1 and TSET corresponding to the current PROFIBUS guidelines.
In some circumstances, older PROFIBUS devices that do not yet work with
response times in accordance with "PROFIBUS DP Expansion for EN 50170
(DPV1)", may provoke telegram repetitions. If this behavior occurs, you can
increase Idle1-Time as an emergency measure. This will, however, increase the
bus cycle time.
The Idle2-Time (TID2) is the idle time between an SDN telegram (send data with
no acknowledge) and the following call telegram. These SDN telegrams are used
for global control services (SYNC, UNSYNC, FREEZE, UNFREEZE, and so on).
This value should be set to 1000 tbit DP.
If TID2 cannot be set directly, you can use the parameter max TSDR. If max
TSDR is greater than TID1, as is shown in the table, the value of max TSDR is
automatically used for TID2.
Highest-Station-Address (HSA): A PROFIBUS Master queries the status of all
stations cyclically up to the address value HSA (1 telegram per cycle). As soon
as one station at an address lower than HSA does not respond, (for example
because it is not connected) the relatively long Slot-Time TSL expires until the
next call telegram is transferred.
If it can be ensured that a station is present at every address including the HSA,
this Slot-Time can be avoided.