Parker PDHX-E Series User Manual page 88

In this example the operator would not power the unit on until ready for the sequence to
begin. The XP1 command enables a single run of sequence No.1 after power on. The XD1
command signifies the start of the definition of sequence No.1 and the XT command signifies
the end of the sequence No.1 definition. When the operator applies power to the positioner,
sequence number 1 will be executed (the motor will turn 10 revolutions in the positive
direction). The sequence can be stopped using the S command or, if necessary, by using the
emergency stop (K command).
Changing a Programmed Sequence
Once a sequence is defined it cannot be redefined until it has been deleted. A new sequence
cannot be downloaded over an existing one.
To change a sequence, it must be deleted from memory and then redefined as a new
sequence using the same number.
First, the sequence must be deleted from memory using the XE command. It will not be
deleted from back-up RAM unless the SV command is used after the XE.
Example:
XE1 erases sequence No.1
The changed sequence should then be entered. It will not be saved to non-volatile memory
until the SV command is issued.
Examining the Contents of a Sequence
If the operator wishes to check the contents of the sequence, he would enter:
1XU1
This would cause the positioner to send the contents of sequence number 1 to the terminal's
screen. The 1 preceding the XU command is the device address which must be present
since the XU command is a "device specific" command. After issuing this command the
following will be displayed on the terminal's screen:
;Sequence 1 is: MN A10 V5 D40000 G
This is the command string that is performed when sequence number 1 is executed.
If the operator does not wish to have the sequence execute on power up, it can be cancelled
by issuing either the XP0 or XZ command.
Sequence no.1 can also be run manually using the XR command.
Sequence Status Requests
Sequence status commands include XC, XSD, XSP, XSR, XSS. The XC command can be
used to verify that the memory in the back-up RAM has not been corrupted in any way since
last power down. The XC command will cause the positioner to send a checksum in the form
of three decimal digits (000 - 255) to the terminal. The checksum may be recorded when
sequences have been defined, so that it may be used for comparison later, such as each time
the positioner is powered up.
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