National Instruments SCXI-1121 - Manual (Page 85)

Chapter 4 Register Descriptions
© National Instruments Corporation 4-3 SCXI-1121 User Manual
Configuration Register
The Configuration Register contains 16 bits that control the functions of the SCXI-1121.
When SS* is asserted (low) and D*/A indicates data (low), the register will shift in the data
present on the MOSI line, bit 15 first, and then latch it when the SCXI-1121 is deselected by
the SS* signal on the backplane. The Configuration Register initializes to all zeros when the
SCXI chassis is reset or first turned on.
Type: Write-only
Word Size: 16-bit
Bit Map:
Bit Name Description
15 CLKOUTEN Scanclock Output Enable—This bit determines whether
the SCANCLK signal from the rear signal connector is
sent out, in inverted form, to the TRIG0 backplane signal.
If CLKOUTEN is set to 1, SCANCLK* is transmitted on
TRIG0. If CLKOUTEN is cleared to 0, SCANCLK* is not
transmitted on TRIG0.
14 CLKSELECT Scanclock Select—This bit determines whether the
SCXI-1121 uses SCANCLK or the inverted form of
TRIG0 to clock the MUXCOUNTER for the purpose of
scanning through the analog channels. If CLKSELECT is
cleared to 0, SCANCLK is used to clock MUXCOUNTER.
If CLKSELECT is set to 1, TRIG0* is used as the source
to clock MUXCOUNTER.
13 SCAL Shunt Calibrate—This bit determines whether the shunt
calibration switches on the SCXI-1321 are closed or open.
If SCAL is cleared to 0, the switches are open. If SCAL is
set to 1, the shunt calibration switches on the SCXI-1321
are closed and an R
SCAL
is placed in parallel with the
bridge between EX+ and CH+ on all four channels.
12-10, 7-6 X Don’t care bits.
15 14 13 12 11 10 9 8
CLKOUTEN CLKSELECT SCAL X X X CHAN1 CHAN0
7 6 5 4 3 2 1 0
X X RTEMP RSVD SCANCLKEN SCANCONEN AB0EN FOUTEN*