Emerson SI-PROFIBUS

86 Unidrive M SI-PROFIBUS User Guide
Issue Number: 3
Table 14.12 CT Single Word Bit Positions
14.6.1 Constructing CT Mode 1 Single Word Read Messages
Figure 14-1 CT Single Word read sequence (Mode 1)
The following example telegrams show how to read the post-ramp speed reference (in
rpm with one decimal places) from Pr 02.001 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
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.
b15 b14 b13 b12 b11 b10 b9 b8
READ ERR
Reserve
d
32-BIT Stamp Number
b7 b6 b5 b4 b3 b2 b1 b0
Data Byte
Bit b15-b12 b11-b8 b7-b4 b3-b0
Value 1001 0001 0000 0010
READ
Start
Send first telegram
to OUT word 0
Read IN
word 0
Tx_Stamp_No =
Rx_Stamp_No?
Send next
telegram to
OUT word 0
Tx_Stamp_No
= 2?
No
Yes
Check status
of ERR bit
1
0
ERROR. Check parameter exists,
data is in correct range, and parameter
is Read/Write
Calculate
data value
END OF
SEQUENCE
Read IN
word 0
Tx_Stamp_No =
Rx_Stamp_No?
Send next
telegram to
OUT word 0
Tx_Stamp_No
= 6?
No
Yes
Send telegram 3 to
OUT word 0
Store data
byte
Yes
No
Yes
No