Diagnostics; Overview; Error Reactions; Fig. 9 Sync/Freeze Functionality - Beckhoff FC3102 Documentation

FC310x as master
• This will start the PROFIBUS cycle
• A Sync/Freeze telegram is sent at the start of the PROFIBUS cycle
• This will cause the Bus Couplers to start a K-bus cycle with the outputs from the last task cycle and
transfer the inputs from the last K-bus cycle
• The master will then send the current outputs to each slave and pick up the transferred inputs
• The inputs are read at the start of the next task cycle
• etc.
Outputs and inputs are therefore always one cycle old.
Fig. 9: Sync/Freeze functionality
On the FC310x, set the Operation Mode on the "FC310x" tab (for TwinCAT 2.8 [} 40] or TwinCAT 2.9
[} 48]) of the master to "DP/MC (equidistant)". At the boxes to be operated via Sync/Freeze, click the flag
Sync/Freeze enable on the Profibus [} 58] tab. The master always uses group 1 for the Sync/Freeze
synchronization.
3.4

Diagnostics

3.4.1

Overview

The Error reactions [} 16] section describes the reactions that will be given to slaves that do not answer or
that answer incorrectly, to a PLC stop or at start-up. The Slave Diagnostics [} 23] chapter explains how
diagnostic data provided by the slave and slave statistics can be read, while the Master Diagnostics [} 20]
chapter describes general diagnostic information and statistics.
3.4.2

Error Reactions

Failure of a slave
If a slave does not respond or the response is faulty, the master repeats the telegram several times until the
Max Retry limit is reached (TwinCAT 2.8: see PROFIBUS [} 42] tab of the master, TwinCAT 2.9: see Bus
Parameter [} 49] dialog). If a faulty telegram is received, the master repeats immediately, in the event of a
timeout the master waits for a response from the slave until the Slot time has elapsed (TwinCAT 2.8: see
PROFIBUS [} 42] tab of the master, TwinCAT 2.9: see Bus Parameters [} 49] dialog). At 12 Mbit/s, a slot
time of 1000 bit-periods and a max retry limit of 4 (default values) then a Data_Exchange telegram will delay
sending the following telegram by
TDelay = (4 x ((15 + number of outputs) x 11 + 1000) - (15 + number of inputs) x 11)/12 µs
The DpState [} 25] of the slave is set to 0x02 (timeout) or 0x0B (faulty telegram). The effect on the DP
connection can be set (see below).
Normal DP cycle (12 Mbit/s, 5 slaves, 20 bytes I, 20 bytes O per slave on average)
16 Version: 3.0 FC3101 and FC3102