SIS Documentation
SIS3820
VME Scaler
Page 67 of 79
15.5.2 arm/enable with MCS
15.5.2.1 enable
Use the key operation enable command for multiscaling with an internal time base (prescaled
internal 10 MHz pulse generator e.g. like in the sis3820_mcs example program). The first
time slice (counting period) will have the same length as consecutive slices this way.
15.5.2.2 arm
Use the key operation arm command for multiscaling with an external time base (LNE
source). By means of the arm/enable source bits of the operation mode register you can define
whether the actual enable will be defined by the LNE front panel signal (with input mode 1,2
or 3 active) or the ChN source. This way your first time slice/counting period will have the
same lengths (angular encoder clock ticks, stepper motor ticks, ...) as consecutive bins.
15.6 Clearing/non clearing mode
The SIS3820 has two sets of counters. The two sets are the actual counters and the „old
counters“. Both counter sets are preset to 0 after a power up/key reset or counter clear.
The actual counter set becomes active with the count enable.
At LNE (or read shadow) following process is initiated depending on the non clearing mode
bit of the acquisition/operation mode register
“non clearing mode” = 0 :
•
the contents of the current counter set is subtracted from the contents of the “old
counter” set (which was latched by the previous LNE/clock shadow) and the
difference is stored in the shadow register set or copied to SDRAM/FIFO
•
the contents of the current counter set is stored to the “old counter” set
“non clearing mode” = 1 :
•
the contents of the current counter set is stored to the shadow register set or copied
to SDRAM/FIFO