Chapter 2
Analog Input Timing/Control
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National Instruments Corporation
2-117
DAQ-STC Technical Reference Manual
SI2_LOAD_SRC
SI2 Load Source—This signal determines which load register, A or B,
the SI2 counter will use on the next reload. The initial SI2 load source is
set using AI_SI2_Initial_Load_Source. The SI2 control logic updates
the load source while the DAQ-STC is counting. The current load source
depends on the counter state and the selected reload mode. Related
bitfields: AI_SI2_Initial_Load_Source.
SI2_SRC
SI2 Source—This signal is the timebase for the SI2 counter. It is equal
to either SI_SRC or AI_IN_TIMEBASE1. Related bitfields:
AI_SI2_Source_Select.
SI2_TC
SI2 TC—This signal is the SCLK signal when internal CONVERT is
selected.
SI_CE
SI Count Enable—This signal enables and disables the SI counter. Refer
to section
, for the SI_CE logic equations.
SI_CLK
SI Clock—This is the actual clock for the SI counter and the SI control
logic. When the counter is not armed, SI_CLK is derived from the write
strobe for AI_Command_1_Register, so that the counter can be loaded
using the load command. When the counter is armed, SI_CLK is the
same as SI_SRC. Related bitfields: AI_SI_Load.
SI_HOLD
SI Hold—This signal controls the SI save register. If SI_HOLD = 0, then
the SI save register tracks the SI counter output. If SI_HOLD = 1, then
the SI save register latches the SI counter output on the next SI_CLK.
SI_LOAD
SI Load—This signal pulses to load the value from the selected SI load
register into the SI counter. Related bitfields: AI_SI_Load.
SI_LOAD_SRC
SI Load Source—This signal determines which load register, A or B, the
SI counter will use on the next reload. The initial SI load source is set
using AI_SI_Initial_Load_Source. The SI control logic updates the load
source while the DAQ-STC is counting. The current load source
depends on the counter state and the selected reload mode. Related
bitfields: AI_SI_Initial_Load_Source.
SI_SRC
SI Source—This signal is the timebase for the SI counter. Related
bitfields: AI_SI_Source_Select.
SI_START1
START1 Synchronized to SI_SRC—This signal is generated by the
hardware by passing the output of the AI_START1 selector through
polarity selection, edge detection, and synchronization (synchronized to
the falling edge of SI_SRC).
Table 2-9.
Internal Signals (Continued)
Signal
Description