FC 68 - Remote Manual Set Constant

The remote manual set constant (RMSC) function code allows the value of a constant to be entered to the control scheme via a console (i.e., operator interface station) or other device such as the plant computer via a network interface unit.

 

When the function block receives this command, an exception report is generated to notify the operator or computer that the value has changed. An exception report is also sent on the loop at the maximum exception report time; or if in the track mode, the value of S6 exceeds the significant change parameter of the segment or module, whichever applies.

 

High and low limits may be set to guard against unreasonable values. Specifications S2 and S3 select the high and low limits and also set the span for significant change. Specification S4 specifies the output value of the controller in normal mode (S5 = 0) on initial startup. The S4 value is updated via a console and is output from the block after a mode change to execute or a reset of the module.

 

Specifications <S5> and <S6> are the block addresses of the track switch and track reference values. The RMSC block can be forced to output the value from <S6> when the track switch <S5> goes to one. An exception report is generated each time the track switch activates or deactivates.

 

Outputs:

Blk

Type

Description

N

R

Last value entered for S4 when <S5> = 0, or value of <S6> when <S5> = 1

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

0

I

Full

Engineering unit identifier

S2

N

100.000

R

Full

High Limit

S3

N

0.000

R

Full

Low Limit

S4

N

0.000

R

Full

Initial output value after addition, modification, power up of block

S5

N

0

I

Note 1

Block address of track switch:

0 = normal

1 = track

S6

N

5

I

Note 1

Block address of track value

 

NOTES:

1. Maximum values are: 9,998 for the BRC-100 31,998 for the HAC

 

68.1 Explanation

 

Figure 68-1 shows an example of a configuration to enable operator intervention in case of temperature transmitter failure. The test quality block (function code 31) outputs a zero as long as the transmitter input is good. The NOT block (function code 33) inverts this to a one and the REMSET output tracks the transmitter until the transmitter fails. At that time, the REMSET is released to the operator.