Black Box IC109A-R2 Specifications download pdf (Page 31)

Defining a Universal Modbus Address for a Point Parameter Value

Honeywell Universal Modbus Interface Reference 31

“Digital” Signal Tag Example:

“Digital” Variable Example:

“Analog” Variable Example:

Digital Output Control Strategies

Some controllers support the use of digital outputs as destination addresses;

however, this functionality may have unintended consequences.

Digital outputs are typically controlled by the controller itself. If you use a digital

output in a destination address, the server value will always override the value the

controller expects to use. Once the output has been “forced” by the server, control

cannot be returned to the controller. (that is, the server value will always have

precedence).

Because of this potential problem, the use of the digital output as a destination

address has been disabled for the UMC800. Instead if you have a control strategy

as shown in “Digital Output Control Strategy - Example 1” on page 31, rather

than use “Digital Output” as the destination of a server point parameter, use the

strategy shown in the “Digital Output Control Strategy - Example 2” on page 32.

This strategy uses two server destination addresses, “Force Value” and “Force

Enabled”. “Force Enabled” enables you to switch between the local value,

“Calculated Value”, and the server value, “Force Value”.

Parameter Source Address Destination Address

PV TAG n Not Configurable

Parameter Source Address Destination Address

PV MATH_VAR n Not Configurable

OP MATH_VAR n MATH_VAR n

Parameter Source Address Destination Address

PV MATH_VAR n Not Configurable

SP MATH_VAR n MATH_VAR n

Figure 9 Digital Output Control Strategy - Example 1

Calculated Value

Digital Output

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 119 120

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Black Box IC109A-R2 Specifications Page 31