User`s guide

Function Blocks
Function Block Categories and Types
80 UMC800 Control Builder User’s Guide Release E
1/01
Block Type Description Graphic Form
WVAR Write Variable – Allows the value of a selected variable to be
changed when enabled.
TAHD Track and Hold - Provides an output that tracks the value of
the input (X) when a digital input signal (TC) is ON; or when
(TC) is OFF, hold the output at the last value of (X).
BCD Binary Coded Decimal Translator - Accepts up to 8 digital
inputs in sequence and interprets the ON/OFF status of the
first 4 inputs as a BCD value between 0 and 9 and the second
4 digits as a value between 10 and 90 for a total range of 0 to
99.
DENC Digital Encoder - This block’s main function is to totalize the
number of ON states from up to 16 digital signals. The block
digitally encodes up to 16 digital inputs to a single floating
point output value.
HOA Hand/Off/Auto Switches - The Hand – Off – Auto (HOA)
switch function block permits state change requests from a
Local Operator Interface or a Remote source. The block
states are: BYPASS (external manual operation of a device),
HAND (manual operation from an operator interface), AUTO
(default – requests are operated automatically), or OFF (relay
to be switched to Bypass, Hand, or Auto). The HOA switch is
also used with the Device Control (DC) function block to
comprise a Pump Control algorithm.
DC Device Control - The Device Control function block is
normally used to control pumps. Based on certain events, the
device will be held in one of six states: READY, PRESTART,
STARTING, RUNNING, STOPPING, DISABLED, or FAILED.
The READY (off state) is the initial state of the function block.