II - DCE FEL ČVUT v Praze

SIMATIC S7 HART Analog Modules
4.8.5 Additional Parameter Data Records
Structure of the
parameter data
records 128 and
129
Notes on the
additional
parameters
4-36
The following figure shows the structure of the additional parameter data
records 128 for channel 0 and 129 for channel 1. The settings affect the
assigned channel.
Byte 0
Byte 1
Byte 2
7 6 5 4 3 2 1 0
Number of repeated attempts
during HART communication
Wire break filter time,
unit: 0.25 seconds (AI HART)
Time required to update
HART variables in user data
area, see Figure 4-20
Unit: 1/4 second
Fig. 4-19 Parameter data records 128 and 129 of the HART analog modules
The additional parameters comprise parameters which you do not normally
need to change, as they have already been set to a optimized value: the
following table provides explanations of the parameters and the default
values.
Table 4-15 Additional parameters of the HART analog module
Parameter Explanation Value range and default setting
Repeated
attempts
Wire break
filter time 1)
If the HART analog modules transmit a command to
the field device and the connection is busy, the set
number of repeated attempts is started.
A wire break is only signaled if it occurs for longer than
the set filter time.
Update time The HART modules send the HART command 1
automatically, to read the present value of the primary
variable.
Value range: 0 to 255,
Default setting: 3,
No repeat attempts: 0
Value range: 0 to 20,
Default setting: 3 0.75 seconds,
No filter time: 0
Value range: 0 to 255,
Default setting: 12 3 seconds,
No waiting time: 0
1) As some measuring transducers take longer than others to start up, you may find that several diagnostic interrupts
are triggered during startup. The wire break filter time was introduced to avoid this problem.
Default parameter
assignment for DP
master class 2
When the HART analog modules have no parameters, for example, after a
power failure, they can obtain default parameters from PROFIBUS-DP
master class 2 while the programmable logic controller is deactivated. This is
done with the aid of parameter data record No. 250 which consists of one
byte with the value unequal 0. However, the assignment of default
parameters can only be initiated when the module is in an unparameterized
state. You can determine the state of the module by reading the diagnostic
data record: see Figure 4-12.
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04