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Bus Parameters Appendix A
The table below defines the bus parameter settings options, shown in the figure. The Unit t
BIT
is defined as the
transmission time for one bit at the selected baud rate.
Item Symbol Description Unit Editable
by User
Baud rate -- Defines the transmission rate on the PROFIBUS-DP Net-
work. The following baud rate values are defined by the
PROFIBUS-DP standard:
•9.6 kBits/s
• 19.2 kBits/s
• 45.45 kBits/s
• 93.75 kBits/s
• 187.5 kBits/s
• 500 kBits/s
• 1500 kBits/s
• 3000 kBits/s
• 6000 kBits/s
• 12000 kBits/s
The default value is 1500 kBits/s.
-- Yes
Optimize -- The Optimize setting defines whether or not selected
parameters can be changed by the user.
• By Standard
Forces the user to use the default (optimized) settings.
•By User
Makes selected fields editable.
Note 1. If the By User option is selected and changes
have been made, it is still possible to switch
between Optimize settings, without the changes
being lost.
2. If the By User option is selected and the baud
rate is changed, the parameters will be opti-
mized to the new baud rate.
-- Yes
Slot Time T
SL
The maximum time a Master Unit must wait for a response
to a request message.
t
BIT
Ye s
Min. Station Delay of
Responders
min T
SDR
The minimum allowed time for a slave station before it will
generate a response to a request message.
t
BIT
Ye s
Max. Station Delay of
Responders
max T
SDR
The maximum allowed time for a slave station to generate
a response to a request message.
t
BIT
Ye s
Quiet Time T
QUI
The time a transmitting station must wait after the end of a
message frame, before enabling its receiver.
t
BIT
No
Setup Time T
SET
The time between an event and the necessary reaction. t
BIT
No
Min. Slave Interval -- The Minimum Slave Interval defines the poll cycle, i.e. the
minimum time between two consecutive Data_Exchange
Cycles to the same slave station. The Minimum Slave
Interval must be smaller than the Target Rotation Time.
ms Yes
Calculated Minimum Slave Interval in milliseconds. ms No
Target Rotation Time T
TR
The anticipated time for one token cycle, including
allowances for high and low priority transactions, errors
and GAP maintenance. Do not the value below the
calculated value, to avoid bus communication interruptions.
t
BIT
Ye s
Max Retry Limit -- Maximum number of request transmission retries by this
master if a station does not reply to a request.
-- Yes
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