User Guide

Program Methodology—Point Status Indicators
Siemens Building Technologies, Inc. 1-77
Point Status Indicators
Point status indicators are used to monitor the current status of
points defined in the device. Point status indicators can be used to
test if a point is at a specific status, and then act accordingly.
Firmware uses syntactical words (ON, OFF, AUTO...) to indicate the
status of a point.
NOTE: Since these points are related specifically to the functions
of the device, point status indicators cannot be used over
the network.
Failed Point Values
If a point in a PPCL statement fails, the statement continues to use
the point's last known value. For example:
MIN(RMMIN,RM1TMP,RM2TMP,RM3TMP)
If RM1TMP is a physical point that fails when it has the lowest value
of the three RMTMP points, the MIN statement will set RMMIN to the
last known value for RM1TMP.
Determining Point Status
Point status indicators can be used with IF/THEN/ELSE commands
to determine the status of a point. When a point is at a specific
status, a certain action is taken.
Example
This example uses an L2SL point to explain the methodology of
testing point status. The point name is LIGHTS and its function is to
control the lights for a large conference room.
The configuration for an L2SL point uses two addresses:
• The first address controls an ON/OFF switch.
• The second address monitors a proof condition. Use of this
address is optional.
APOGEE PPCL User’s Manual
1-78 Siemens Building Technologies, Inc.
To verify that the lights are ON in the conference room, you could
use the following test:
740 IF (LIGHTS.EQ.ON) THEN ...
When this line of code is executed, the status of LIGHTS is checked
to see if it is ON. If the point status equals ON, then a particular
action occurs. If the point status does not equal ON, an alternate
action occurs.
Commanding and evaluating the HAND status
Some Point Termination Modules (PTMs), Modular Equipment
Controllers (MECs), and Point Expansion Modules (PXMs) have an
optional HAND-OFF-AUTO (HOA) manual override switch that
enables you to control equipment at the field panel.
CAUTION:
The HOA override switch is not to be used as a
safety device when performing maintenance. If the
HOA switch is used as a safety device, it can result
in serious injury to personnel or cause damage to
property or equipment. Always follow safety
procedures when performing maintenance.
The HAND status identifies a point being controlled by an HOA
manual override switch and not the system. The HOA override
switch is only method you can use to control whether a point is
placed into or taken out of HAND status.
• Points cannot be commanded to HAND by using an operator
interface.
• Points cannot be commanded to or removed from HAND status
by using program statements.
Before attempting to command points that contain HOA override
switches, check the status of the PTM or MEC to ensure that the
point can be commanded.
The HAND status appears as part of the overall point status. This
status indicates that an HOA override switch is controlling a piece of
equipment. The equipment cannot be controlled through the operator
interface or PPCL until the HOA override is switched back to the
AUTO position.