ProSoft Technology CLX-PVX - Manual (Page 29)

QTS-CLX-PVX Page 23
Accessing I/O Data
Required Connections
In master mode, the QTS-CLX-PVX does not begin scanning the I/O bus until all
ControlLogix connections to the module are present.
If the connection is later closed, the QTS-CLX-PVX continues scanning the bus. Inputs
do not update in the ControlLogix while the connection is closed and outputs do not
update.
In monitor mode, the module does not wait for ControlLogix connections.
Data Updates
It is important to remember always that the PROVOX Control I/O bus updates data only
when the data changes.
Any changes that occur when the module is not connected to the bus will not be captured.
Discrete Data
Use the aliases created by ClxPvxCfg to access discrete data to ensure that you are using
the correct address and bit.
Analog Data Format
Analog values on the Control I/O bus are expressed in PROVOX Percent Format. The
number is shown in the PROVOX controller as a percent with 3 decimal places. The
range is -13.969% to +113.970%.
Each 16-bit word consists of:
upper byte = signed byte, represents the whole number part of the percentage
lower byte = unsigned byte, represents the fractional part, as a fraction of 256
Some examples:
Number, percent High byte, hex Low byte, hex Number, hex
-13.97% F2 08 F208
-1.75% FE 40 FE40
0.00% 00 00 0000
1.75% 01 C0 01C0
25% 19 00 1900
25.25% 19 40 1940
50% 32 00 3200
75% 4B 00 4B00
100% 64 00 6400