User Guide

Program Methodology—Converting a Sequence of Operation into
Program Code
Siemens Building Technologies, Inc. 1-105
Program Documentation
Programs should have documentation that identifies the program
functions and the equipment being controlled. Fortunately, the
modular programming method makes an easier task of
documentation.
The following documentation methods are described in more detail
on the following pages:
• Internal documentation
• External documentation
One or more of these methods can be used to document program
operation. In addition, you can use these documentation methods as
planning tools when designing a PPCL program.
Internal documentation
Internal documentation refers to information written into the program
using comment lines.
• Comment lines allow you to enter text information describing the
functionality of a specific section of code.
• Comment lines are especially helpful for describing subroutines
and areas of program code that are difficult to understand.
You must enter the letter C after the line number to prevent the
program from interpreting your comments as program commands.
For example:
200 C THIS COMMAND WILL TURN ON SFAN01
210 C IF RMTEMP VALUE FALLS BELOW 68 OR
220 C RISES ABOVE 78. SFAN01 WILL REMAIN
230 C ON/OFF FOR AT LEAST 5 MINUTES.
NOTE: The device and software used to program PPCL
determines how comment lines must be entered. For
more information on using comment lines, see the user's
manual for the device or software you are using.
APOGEE PPCL User’s Manual
1-106 Siemens Building Technologies, Inc.
External documentation
External documentation refers to physical control diagrams, layouts,
and information written about the program. This information can be
used as a reference to learn about the functions of the control
system. The following two methods are commonly used for external
documentation:
• Decision tables
• Pseudocode
Decision tables
Decision tables provide a visual representation of how a specific
piece of equipment interacts with other equipment during each mode
of operation. Like truth tables, a decision table defines inputs that are
logically compared to produce outputs (results).
• Inputs for a decision table are the types of equipment and all
possible modes of operation.
• In each row of the table, a piece of equipment is compared to
each mode of operation to determine the status of that equipment
during the mode.
Table 1-11 provides an example of a decision table that defines six
pieces of equipment and four modes of operation.
Table 1-11. Example of a Decision Table.
Modes of Operation
Equipment type Shutdown Day mode Smoke Warm-up
Supply Fan Off On On On
Return Fan Off On On On
CC Valve Closed Modulate Modulate Closed
Mixing Dampers Closed Modulate Modulate Closed
Supply Fan Vol Modulate Modulate Open Modulate
Return Fan Vol Modulate Modulate Open Modulate