Siemens Simatic PCS 7 Commissioning Manual page 38

Engineering
4.3 Parameter assignment
Bus parameters Setting range (default)
Maximum 16
Scheduling
Overhead
Max Inter Chan 0 - 7
Signal Skew (0)
Post Trans Gap 0 - 7
Extension (0)
Default 32 - 32767
Minimum Token
(86)
Delegation Time
Default Token 276 - 65000
Holding Time
(276)
Target Token 1 - 60000
Rotation Time
(60000)
Link 292 - 65000
Maintenance
(336)
Token Holding
Time
Time 10 - 55000
Distribution
(5000)
Period
38
Meaning and limiting values
This parameter extends the time that may be used by the LAS for processing
the schedule. The parameters unit is the transmission duration of one octet.
The following times should be included in the duration:
● The time allocated for each scheduled activity
● The time to determine whether a device on the FF segment can serve as an
LAS.
● The time for the organization of the schedule.
The parameter will be checked with the configured value in the LAS domain
during downloading of the FF segment.
The minimum value for this parameter is determined by the maximum value of
all the LAS-capable FF devices in the FF segment.
This parameter indicates the maximum permitted time offset of the data that a
device receives from several ports (redundant routes) via an H1 connection.
Select a value between 0 and 7 4-bit transmission times.
The value range is (0 .. 7) * 4 * Tb.
Selection: 0 to 7
There will be an interruption of the signal transmission in 4-bit transmission times
after each transmission.
Use this parameter to increase this interruption in signal transmission by
additional 4-bit transmission times. The value range is (0 .. 7) * 4 * Tb.
A value greater than 0 increases PerDlpduPhlOverhead.
Selection: 0 to 7
The time required for an FF device to process all tasks. The parameters unit is
the transmission duration of one octet.
Keeping to the schedule (controlled by LAS ) has the highest priority on the FF.
The time available for an FF device should be sufficiently dimensioned (greater
than Default Token Holding Time).
An FF device can only be processed if it keeps the token for longer than
stipulated by the "Default Minimum Token Delegation Time" parameter.
Time period assigned to an FF device by the LAS for the following tasks:
● acyclic bus traffic
● System Management
● Alarms and events
Within this time all FF devices must have received the token for acyclic data
transfer once. If the actual token rotation time is higher than the configured value
for Target Token Rotation Time, the LAS will increase the token priority.
A Target Token Rotation Time value that is too small causes the failure of low-
priority services. The following are low-priority services:
● System Management
● acyclic bus traffic (client-server connections)
Period of time which the LAS uses within a token rotation for checking a link.
This time period contains the following processes:
● find new FF devices
● send LAS status telegrams
Time period for forwarding time service telegrams (in milliseconds)
Time distribution PDU's will be sent on the bus in 95% or less of that time period.
FOUNDATION Fieldbus
Commissioning Manual, 03/2013, A5E03880935-02