User Manual

Using Modbus RTU 4-7
20-COMM-H RS-485 HVAC Adapter User Manual
Publication 20COMM-UM009D-EN-P
Table 4.F shows the register outputs. These outputs must be used for writing
multi-bit commands and the Reference.
Viewing the Logic Status and Feedback
On Modbus RTU, there are two ways to view the logic status: discrete
inputs (Table 4.G
) and register inputs (Table 4.H on page 4-8). You can use
discrete inputs when you need to view only one bit in the logic status word.
For example, to view whether a PowerFlex 70/700 drive is Ready (bit 0),
you can use a discrete input (Modbus Address 1x0001).
When you need to view multi-bit fields in the logic status word or to view
the entire logic status word, you must use a register input to maintain data
integrity. For example, to view the local control of a PowerFlex 70/700
drive (bits 9…11), you must use a register input (Modbus Address 3x0001).
To view the Feedback, you must also use a register input (Modbus Address
3x0002 and/or 3x0003). For details about how the feedback is scaled, refer
to the Setting the Logic Command and Reference
on page 4-5.
Table 4.G
shows that there are 16 discrete points to represent the status
word bit by bit. These points can be used only for reading single-bit status.
Table 4.F Logic Command and Reference: Register Outputs
Modbus
Address Output Description Values
4x0001 Product Logic Command 16-bit word. Bit definitions for PowerFlex 70/700 drives are in
Table 4.E
. For other products, refer to their documentation.
4x0002 Reference Lo Bit 0…15 of 32-bit reference.
4x0003
(1)
(1)
The reference value is sent only when accessing address 4x0003. If a 32-bit reference is used, the 32-bit value
will be merged together by register 4x0002 and 4x0003 when accessing address 4x0003.
Reference Hi Bit 16…31 of 32-bit reference or the whole 16-bit reference.
Table 4.G Logic Status: Discrete Inputs (to Controller from Drive)
Modbus
Address Logic Status Bit
PowerFlex 70/700 Example
Description Values
1x0001 0 Ready 0 = Not Ready
1 = Ready
1x0002 1 Active 0 = Not Running
1 = Running
1x0003 2 Command Direction 0 = Reverse
1 = Forward
1x0004 3 Actual Direction 0 = Reverse
1 = Forward
1x0005 4 Accel 0 = Not Accelerating
1 = Accelerating
1x0006 5 Decel 0 = Not Decelerating
1 = Decelerating
1x0007 6 Alarm 0 = No Alarm
1 = Alarm
1x0008 7 Fault 0 = No Fault
1 = Fault
1x0009 8 At Speed 0 = Not At Reference
1 = At Reference