02/04/2020


The text here was copied from a picture of a page in the command dictionary (a 3-ring binder) sent by JPL.



DESTINATION

FDS



EFFECT ON SPACECRAFT

The SC21AG command sets a flag in the FDS which controls the
sending of discrete pulses to the CRS.  With CRS power on,
reception of the FDS pulse will turn on the intrument's high voltage.



MNEMONIC AND TITLE

Mnemonic: SC21AG
Title:    CRS HV FLG



TELEMETRY INDICATIONS

To verify that the HV flag is set, check that HV is off, send SC21AG,
and then check to see that HV turns on. Observe S-379, CRS Status
Word 0, bit 7, to determine whether HV is on (bit = 1) or off (bit = 0).



FUNCTION AND COMMAND BIT STRUCTURE

To turn on the CRS high voltage, a pulse must be received from FDS
over the CRS HV ON line.  This pulse is generated every 96 s by the
FDS but is output only when the HV ON flag is set.  When the flag is
set, one pulse is allowed to pass to the CRS, thereby turning on HV
and resetting the flag automatically.  Resetting the flag inhibits the
pulses; it does not turn off CRS HV, (CRS HV is turned off by turning
off the power to CRS (21AR).