Register Descriptions
Chapter 4
SCXI-1160 User Manual
4-4
© National Instruments Corporation
Data Register
The Data Register contains 32 bits that control the state of each relay of the SCXI-1160.
Whenever the Address Handler selects the Data Register, the Data Register shifts in the data
present on the MOSI line, bit 31 first, and then latches the data when it is deselected. At power
up or reset, the Data Register content is unknown and its outputs are not driving the relay coils.
The Data Register address is hexadecimal 0001. Table 4-2 shows a truth table for setting and
resetting a given relay.
Table 4-2. Truth Table for Resetting and Setting Relays
NC(x) (Reset)
NO(x) (Set)
Function
0
0
1
1
0
1
0
1
No change
COM connects to NO position
COM connects to NC position
Not valid
Type:
Write-only
Word Size:
32-bit
Bit Map:
31
30
29
28
27
26
25
24
NC(15)
NC(14)
NC(13)
NC(12)
NC(11)
NC(10)
NC(9)
NC(8)
23
22
21
20
19
18
17
16
NC(7)
NC(6)
NC(5)
NC(4)
NC(3)
NC(2)
NC(1)
NC(0)
15
14
13
12
11
10
9
8
NO(15)
NO(14)
NO(13)
NO(12)
NO(11)
NO(10)
NO(9)
NO(8)
7
6
5
4
3
2
1
0
NO(7)
NO(6)
NO(5)
NO(4)
NO(3)
NO(2)
NO(1)
NO(0)
Bit
Name
Descripion
31-16
NC<15..0>
Normally Closed (x) – These bits determine the state of the
relays. If set to 0, the relays stay in their previous positions
or respond to the NO(x) state. If set to 1 and the NO(x) is
set to 0, the NO position on the relay opens and the COM
connects to the NC position.
15-0
NO<15..0>
Normally Open (x) – These bits determine the state
of the relays. If set to 0, the relays stay in their previous
positions or respond to the NC( x). If set to 1 and the NC( x)
is set to 0, the NC position on the relay opens and the COM
connects to the NO position.
Note: A value of NC(x) = 1 and NO(x) = 1 is not valid. x indicates a given relay number.