Manual

3-78 Detailed Descriptions of ACL Commands
XU <id>, <value> [, <which> ] Execute Until
This command invokes a Download Sequence in the same way as the XD ("Execute
Download Sequence") command, except that XU repeats the Download Sequence until a
specified condition exists on the Digital Inputs or in an ACL variable. Any repeat count
specified in the BD command is ignored.
(The discussion below assumes that the Digital Inputs are being tested. For information
about testing ACL variables, please see the VT, V<, V=, and V> commands, as well as
Chapter 10.)
<id> is the identifying number (0 through 255) of the Sequence to be repeated. This is like
the <id> parameter of the XD command.
<value> and <which> establish the condition to be tested after each execution. They are
identical in meaning to the <value> and <which> parameters of the WN command. That is,
<value> specifies the values to compare against the Digital Inputs, and <which> specifies
which Digital Inputs to check and which to ignore.
<which> is optional. If omitted it defaults to 255, meaning that all eight Digital Inputs are
checked.
The Digital Inputs are tested after each execution of the Download Sequence. If the
condition is met the Download Sequence quits repeating and execution resumes with the
ACL command following the XU command. If the condition is not met the Download
Sequence is repeated one more time, and the test is made again. Thus the XU command
always executes the Download Sequence at least once.
For information about debouncing and signal sense (High True vs. Low True) see Chapter 8
Using the Digital Outputs and Inputs.
Example: suppose your application is to drill several holes in a block of wood. Download
Sequence 27 contains the commands to pull the drill bit out of the hole, turn on compressed
air to blow away the chips, and plunge the drill back into the hole. A microswitch detects if
the drill has gone all the way through the wood yet. Assuming that the microswitch is
connected to Digital Input 0, you might use XU 27, 1, 1; to repeat the cycle until a hole is
finished. Then you could move the carriage to another location and do another XU 27, 1,
1; to drill another hole.
XW <id>, <value> [, <which> ] Execute While
This command repeats a Download Sequence in the same way as the XU ("Execute Until")
command, except that the termination condition is slightly different. As with XU, any repeat
count specified in the BD command is overridden.
(The discussion below assumes that the Digital Inputs are being tested. For information
about testing ACL variables, please see the VT, V<, V=, and V> commands, as well as
Chapter 10.)