Controller Modes - Honeywell 900U02-0100 User And Installation Manual

Execution sequence
 The type of control functions executed during a scan is determined by the system
configuration.

Controller configurations contain a series of algorithms in the form of function blocks that
get executed in a fixed sequence. The first 100 function blocks are pre-assigned by the
system to handle communication tasks, alarm processing, system monitoring functions, etc.
and cannot be changed by the user. Starting with function block number 101, the user may
select the type of function to be executed.

The sequence of function block execution is initially determined by the sequence in which the
function blocks are placed on the graphic diagram in HC Designer.

Final desired sequence must be set by the user to achieve proper and optimum performance.
CAUTION
Incorrect execution sequences can contribute to delays in processing outputs and/or improper
or unexpected operation.

The ControlEdge HC900 controller samples all inputs before the start of a controller scan.

Each input being used in the configuration must be assigned to a function block. The
sequence order of the function block determines when in time the actual value will be
updated. It is important that algorithms that need updated input values for their
calculations have the inputs execute first in the sequence.

Except for Time Proportioning Output (TPO), Three-Position-Step-Control (TPSC) and
Position Proportional Output (PPO) function block types that update their physical output
values while the function blocks are being executed, all physical outputs are updated at the
end of a scan.
8.4.

Controller Modes

The ControlEdge HC900 Controller includes three operating modes. The purpose of each mode is
described immediately below, and salient characteristics of each are described in Table 24. The functions
of the Mode Switch are described in
168 ControlEdge HC900 Process & Safety Controller User and Installation Manual Revision 10
May 2019