Honeywell HC900 - Page 30

Design and Implementation of HC900 Control System - Allowable Function Blocks for Process and Safety Functions
22 HC900 Process & Safety Controller Safety Manual Revision 1.9
01/14
2 Input OR
Monitors two digital input signals (X, Y) to set state of
digital output signal (OUT). If X = OFF and Y = OFF,
then OUT = OFF. If X = ON and/or Y = ON, then:
OUT = ON.
X
X
4 Input OR
Turns digital output (OUT) OFF when inputs X1
through X4 are OFF. Thus, if input X1 or X2 or X3 or
X4 are ON, then: OUT = ON. If all inputs are OFF,
then: OUT = OFF.
X
X
8 Input OR
Turns digital output (OUT) OFF when inputs X1
through X8 are off, thus: If input X1 or X2 or X3 or X4
or X5 or X6 or X7 or X8 are ON, then: OUT = ON. If
all inputs are OFF, then: OUT = OFF.
X
X
Exclusive OR
Turns a digital output signal (OUT) ON only if one of
two digital input signals (X, Y) is ON. Otherwise, the
output is OFF.
X
X
NOT
Reverse state of a digital input (X).
X
X
Digital Switch
Sets the output of the block equal to either input A or
Input B depending on the value of input SA. If input
SA (Select A) is ON, then OUT = Input A, otherwise
OUT = Input B.
X
X
Trigger
Turns a Logic output (OUT) ON for one logic scan
cycle, when a logic input (^) goes from OFF to ON. If
X = ON and previous value of X was OFF, then: OUT
= ON (one scan). Otherwise, OUT = OFF.
X
X
Selectable
Trigger
This block allows you to select one of the following
input conditions for triggering the digital output. - The
input state changes from OFF to ON. - The input state
changes from ON to OFF. - Both of the above. When
this block is "triggered" its output will be ON for one
cycle. This block will also allow you to select one of
the following "initial scan" behaviors:
- No trigger action following a Cold Start or Warm
Start
- Trigger the output on the initial scan following a
Cold Start; takes precedence over the input pin
conditions.
- Trigger the output on the initial scan following a
Warm Start; takes precedence over the input pin
conditions.
- Trigger the output on the initial scan following a Cold
Start or Warm Start; takes precedence over the input
pin conditions.
X
X
Latch
Latches output (OUT) ON when latch input (L) turns
ON and maintain latched output until unlatch input (U)
turns ON. Note that latch input must be OFF for
unlatch input to work. If U = ON, then: OUT = OFF. If
L = ON, then: OUT = ON. Else, OUT = Previous
State.
X
X