Delta Controls DNS-24, Application Manual

Page: 37 / 43

Delta Controls
Document Edition 4.2 Page 37 of 43
APPENDIX A: Programming Notes
The following provides additional important programming information.
1. C
ONFIGURATION
V
ARIABLES
(AV12 & AV21-23): These variables should never be
commanded on the fly from a GCL+ program (or user command). They must be
configured in the proper sequence and they radically alter operation too much to make
frequent changes. Besides, changing the application configuration from an OWS requires
that you reset the BACstat (either locally or via user command). Also refer to the
Configuration Menu options on page 4 for further information.
2. C
OMMANDING
V
ARIABLES
: When commanding other variables (such as setpoints and
alg mode) from GCL++ in an Application Controller write your programs so they are not
being commanded on every program scan. Use
IFONCE or DOEVERY statements to key
the execution of specific events or time intervals, and thereby limit the frequency of such
commands. Otherwise you will create excessive network traffic.
3. C
OMMAND
P
RIORITY
: Both GCL+ programs and user commands (i.e., manual mode)
have the same write priority for all objects in a BACstat. There are no priority arrays or
command hierarchy. Whatever commands the object last is the value the object will have.
Therefore, write your GCL+ programs so as to minimize any conflicts with acceptable
user commands (such as temporary or fixed overrides).
4. GCL++ P
ROGRAMMING TO
R
ESET THE
K
EY
P
RESS
V
ALUE TO
0: Normally the
KeyPress value (AV4) only changes when a new button or button-combination is pressed,
and under these conditions it is not possible to detect that the same button has been
pressed again. With Release 3 (and higher) firmware you can now reset the KeyPress
value after you have read it, allowing you to detect when the same button gets pressed
again. The following is an example of resetting the KeyPress value back to zero (using a
mapped AV in the DAC), assuming you have already read the value.
AV104 = 0
[where AV104 is the mapped AV in the DAC associated with AV4 in
BACstat #1]