Series EJ, ET, EY, FJ & FR
102002-177 Rev M2
46
\1020\02177M2.doc 17 Jun 2019
SET COMMAND (“S”) AND ACKNOWLEDGE (“A”) RESPONSE
Prior to sending a Set Command that performs any function other than a Power
Supply Reset, the computer should ensure that no fault conditions are existing within
the power supply. This is done by first sending a Query Command and examining
the returned Response Packet.
Note that it is legal to send a Set Command that does not assert any of the three
digital controls. For example, if the HV was on and it was desired to change one or
more of the two analog controls, a command packet could be sent containing the new
values for the analog controls but with the three digital control bits set to 0. In this
case, the analog values will be changed and the HV will remain on.
If any of the analog monitor fault bits are active, the Set Command packet must
include a Power Supply reset assertion.
The protocol for the Set Command is as follows:
The power supply receives the “S” command and performs a checksum comparison
and other error checking. If a communication or other error is detected, the power
supply will not execute the command but will send an error message back to the
computer. If the checksum compares properly and no other errors exist, the power
supply will execute the Set Command and return a simple 2 byte Acknowledge
message. The computer should then Query the power supply to be sure that the
power supply parameters are set as desired.
The data will be ASCII encoded, where scaling is done in the Customer computer.
The resolution for the four analog controls is 12 bits, so full scale will be represented
by FFF hex. The first byte “SOH”, can be entered at the keyboard by the
“CONTROL-A” key combination (“CTRL-A”).
All alphabetical entries should use CAPITAL letters only. Use of lower case letters
will result in errors.
The byte definitions of the command message are shown in Table 6. Note that high
order bytes are sent first.
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