Emerson SI-PROFIBUS

90 Unidrive M SI-PROFIBUS User Guide
Issue Number: 3
14.6.2 The parameter re-assembled
The completed value can be assembled as follows to give the complete value as read
from the parameter.
Speed = (High byte * 2
24
) + (Mid-high byte * 2
16
) +
(Mid-low byte * 2
8
) + Low byte
= (0 * 16777216) + (1 * 65536) + (37 * 256) + 220
= 75228
= 7522.8 rpm
14.6.3 Writing parameters using CT Single Word
To write to a 32-bit parameter using the non-cyclic channel, the following telegrams
must be sent one telegram per network cycle to construct the final message.
• Telegram 1 - define menu number
• Telegram 2 - define parameter number
• Telegram 3 - send high data byte
• Telegram 4 - send mid-high data byte
• Telegram 5 - send mid-low data byte
• Telegram 6 - send low data byte
Figure 14-2 CT Single Word write sequence
The following telegrams show how to set the digital speed reference 1 (Pr 01.021) to
12553.9 rpm (32-bit value is 125539) in the drive.
Start
Send first telegram
to OUT word 0
Read IN
word 0
Tx_Stamp_No =
Rx_Stamp_No?
Send next
telegram
Tx_Stamp_No
= 6?
No
Yes
No
Yes
Check status
of ERR bit
1
ERROR
Check parameter
exists, and that it is
a Read/Write
parameter
Parameter
written OK
END OF
SEQUENCE
WRITE