40
SI-INTERBUS User Guide
Issue Number: 1
8.1.5
The parameter re-assembled
The parameter value can be assembled as follows to give the complete value as read
from the parameter.
32-bit access
Pr
2.001
= (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
16-bit access
Pr
2.001
= (high byte * 2
8
) + low byte
= (37 * 256) + 220
= 9692
= 969.2 rpm
When using 16-bit mode, in this example, as Pr
2.001
is a 32-bit parameter, only the
lower two bytes are returned, resulting in an incorrect value being read.
8.1.6
Writing parameters using CT Single Word
To write to parameters using CT Single Word non-cyclic channel, the following
“telegrams” must be transmitted 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 (32-bit) or low data byte (16-bit).
•
Telegram 5 Send mid-low data byte (32-bit).
•
Telegram 6 Send low data byte (32-bit).
shows the normal sequence for writing a
parameter value using CT Single Word non-cyclic.
