Revision 1.9 HC900 Process & Safety Controller Safety Manual 17
01/14
Design and Implementation of HC900 Control System
Refer Installation guide section “Design and implementation”
Allowable Function Blocks for Process and Safety Functions
The following table lists the function blocks which are allowed in the safety portion and the function blocks
which are allowed in the process control portion of an HC900 controller configuration.
Table 4 – Function Blocks
Category and
Function block
Name
Description of Function
Can FB
be used
in a
safety-
related
function?
Can FB
be used
as a
process
control
FB?
FB that
can’t be
used in
safety
config-
uration
I/O Blocks
X
Analog Input
Reads value of an Analog Input from a specified
physical I/O address.
X X
Analog Input with
Remote Cold
Junction
This block is used only for Thermocouples when the
thermocouple Cold Junction is in a remote location,
i.e, NOT connected at the AI module.
X X
Analog Input with
Voting
Reads values of up two to three Analog Inputs from
specified real I/O addresses. Function block value
reflects channels that are within tolerance (3%) of
each other.
X X
Analog Output
The output range high and range low values (0-20
max) set the milliamp output values that correspond
to the 0 to 100% span limits of the inputs.
X X
Analog Output
with Feedback
The output range high and range low values (0-20
max) set the milliamp output values that correspond
to the 0 to 100% span limits of the inputs. Feedback
channel validates physical output is within tolerance
(3%)
X X
Discrete Input
Provides the digital status of a digital input point and
provides interface to other algorithms and functions.
X X
Discrete Input
with Voting
Provides the digital status of a digital input point and
provides interface to other algorithms and functions.
Compares up to three inputs, function block output
reflects the majority of valid input channels. Physical
input channels must be the same model no.
X X
8 Point Digital
Input
Provides read access for up to 8 physical digital
inputs (all read at the same time).
X
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