Fifo register – National Instruments SCXI-1120 User Manual
Page 71
Register Descriptions
Chapter 4
SCXI-1120 User Manual
4-8
© National Instruments Corporation
FIFO Register
The FIFO Register is used to add entries to the Slot 0 FIFO. The FIFO contains the Slot 0 scan
list. Each entry contains a slot number to be accessed, and a count number to determine the
number of samples to be taken from that slot. To write to the FIFO Register, follow the
procedure given in the Register Writes section in Chapter 5, Programming, using 14 as the slot
number, and writing 16 bits to the FIFO Register. The register will shift in the data present on
the MOSI line, bit 7 first, when Slot 14 is selected by the Slot-Select Register. The Slot 0 scan
list is created by consecutive writes to the FIFO Register. Each write creates a new entry at the
end of the scan list. The maximum number of entries is 256. To clear the FIFO of all entries,
clear the HSRS* bit in the HSCR.
Type:
Write-only
Word Size:
16-bit
Bit Map:
15
14
13
12
11
10
9
8
X
X
X
X
X
MOD3
MOD2
MOD1
7
6
5
4
3
2
1
0
MOD0
CNT6
CNT5
CNT4
CNT3
CNT2
CNT1
CNT0
Bit
Name
Description
15-11
X
Don't care bits – Unused.
10-7
MOD<3..0>
Module Number – The value of these bits plus one
determines the number of the slot to be accessed for
this scan entry. For example, to access Slot 6,
MOD<3..0> would be 0101.
6-0
CNT<6..0>
Count – The value of these bits plus one determines
how many samples will be taken before the next
scan list entry becomes active. A value of zero
corresponds to one sample and a value of 127
corresponds to 128 samples.