Chapter 4
Register Descriptions
© National Instruments Corporation
4-3
SCXI-1120 User Manual
Configuration Register
The Configuration Register contains 16 bits that control the functions of the SCXI-1120. 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-1120 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:
15
14
13
12
11
10
9
8
CLKOUTEN
CLKSELECT
X
X
X
CHAN2
CHAN1
CHAN0
7
6
5
4
3
2
1
0
X
X
RTEMP
RSVD
SCANCLKEN
SCANCONEN
AB0EN
FOUTEN*
Bit
Name
Description
15
CLKOUTEN
Scan Clock 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
Scan Clock Select – This bit determines whether the
SCXI-1120 uses SCANCLK or the inverted form of TRIG0
to clock the MUXCOUNTER for the purposes 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.
13-11, 7-6
X
Don't care bits – Unused.
10-8
CHAN<2..0>
Channel Select – These bits determine the channel number
(zero to seven) that is loaded into the MUXCOUNTER to
determine the analog channel to be read during a single
read, or the starting channel on the module for a scanned
data acquisition. CHAN2 is the MSB.
