Honeywell UDC2500 manual Using a Computer Setpoint Overriding Controller Setpoint, Shed

Modbus Read, Write and Override Parameters plus Exception Codes

10.6 Using a Computer Setpoint (Overriding Controller Setpoint)

Overview

You can use a setpoint generated from the computer to override the setpoint being used by the controller. The value generated by the computer will have ratio and bias applied by the controller.

Register Addresses

Use the identifying code in Table 10-7to enter the computer setpoint.

Table 10-7 Computer Setpoint Selection

Parameter	Register		Data	Access	Data Range or
Description	Address		Type		Enumerated Selection
	Hex	Decimal
Computer	007D	125	FP	R/W	Value from computer with
Setpoint					Ratio and Bias applied by
					the controller. Within the
					Setpoint Range Limits in
					Engineering Units or
					Percent.

Shed

The computer setpoint override will continue until SHED from communications occurs or the controller is placed into monitor mode through communications. Doing periodic SLAVE READS within the shed time will allow the override to continue until communication is stopped and shed time elapses. Does not apply to IR communications.

ATTENTION

0 Shed (code 79) allows the override to continue indefinitely or until the reset shed timer register address 1B90 is written using function code 6 or register address 7F using function code 21. Any data value can be written because it is ignored.

When SP is overridden, the upper display becomes “COM” momentarily, and the lower display shows the CSP value as CSXXXX.

			Table 10-7.1 Shed Timer Reset
Parameter	Register			Data	Access	Data Range or
Description	Address			Type		Enumerated Selection
	Hex	Decimal
Shed Timer	7F	127		FP	W	Exit Slave Mode
Reset						IR Only

194 UDC2500 Universal Digital Controller Product Manual 4/07