Leroy-Somer digitax st User Manual page 35

8.7.1 Constructing CT Mode 1 Single Word Read Messages
Figure 8-3 CT Single Word read sequence (Mode 1)
Send first telegram
to OUT word 0
Tx_Stamp_No =
Rx_Stamp_No?
Tx_Stamp_No
Check status
ERROR. Check parameter exists,
data is in correct range, and parameter
The following example telegrams show how to read the post-ramp speed reference (in
rpm with one decimal places) from Pr 2.01 on the drive.
TELEGRAM 1
The first telegram from the PROFIBUS-DP master indicates a READ with stamp
number 1. The data byte contains the menu number of the parameter that is to be read.
Example telegram
Bit
Value
Data word = 0x9102
Stamp number = 1
Menu = 2
When the first telegram has been received and processed in the slave node, it is
mirrored in the non-cyclic IN word back to the PLC. This is the signal to the master
controller program that the first telegram of the message has been received and
understood the second telegram can now be transmitted.
Example response
Bit
Value
Data word = 0x9102
Stamp number = 1
If a telegram produces an error at any point in the sequence the reply to the master will
NOTE
have the error bit ERR set to a 1.
SM-PROFIBUS DP-V1 User Guide
Issue : a
Start
READ
Read IN
word 0
No
Yes
Send next
No
telegram to
= 2?
OUT word 0
Yes
0
of ERR bit
1
is Read/Write
b15-b12
1001
b15-b12
1001
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Send telegram 3 to
OUT word 0
Read IN
word 0
Tx_Stamp_No =
Rx_Stamp_No?
Yes
Store data
byte
Tx_Stamp_No
= 6?
Yes
Calculate
data value
END OF
SEQUENCE
b11-b8 b7-b4
0001 0000
b11-b8 b7-b4
0001 0000
No
Send next
No
telegram to
OUT word 0
b3-b0
0010
b3-b0
0010
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