Chapter 2
Analog Input Timing/Control
DAQ-STC Technical Reference Manual
2-116
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National Instruments Corporation
SCLKG
Internal Sample Clock—SCLKG is the signal that appears on the
CONVERT and PFI2/CONV pins. The hardware generates SCLKG by
passing the SCLK signal through pulsewidth and polarity-selection
circuitry. If the CONVERT pin is configured for high impedance, this
signal will be ground. Related bitfields: AI_CONVERT_Output_Select,
AI_CONVERT_Original_Pulse, AI_CONVERT_Pulse_Timebase,
AI_CONVERT_Pulse_Width.
SC_LOAD
SC Load—This signal pulses to load the value from the selected SC load
register into the SC counter. Related bitfields: AI_SC_Load.
SC_LOAD_SRC
SC Load Source—This signal determines which load register, A or B,
the SC counter will use on the next reload. The initial SC load source is
set using AI_SC_Initial_Load_Source. The SC control logic updates the
load source while the AITM is counting. The current load source
depends on the counter state and the selected reload mode. Related
bitfields: AI_SC_Initial_Load_Source.
SC_SRC
SC Source—The SC source is the timebase for the SC and DIV
counters. In the internal CONVERT mode, SC_SRC is the same signal
as SI2_SRC. In the external CONVERT mode, SC_SRC is equal to
SCLK. The external trigger and gate inputs, which are not generated
synchronous to the SC source outside of the AITM, can and should be
synchronized to the SC source inside of the AITM.
SC_START1
START1 Synchronized to SC_SRC—This signal is generated by the
hardware by passing ADR_START1 through the master/slave trigger
circuitry.
SC_TC
Scan Counter TC—This signal indicates to the counter control logic that
the programmed number of scans has been generated.
SI2_CE
SI2 Count Enable—This signal enables and disables the SI2 counter.
Refer to section
, for the SI2_CE logic equations.
SI2_CLK
SI2 Clock—This signal is the actual clock for the SI2 counter and the
SI2 control logic. When the counter is not armed, SI2_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,
SI2_CLK is the same as SI2_SRC. Related bitfields: AI_SI2_Load.
SI2_LOAD
SI2 Load—This signal pulses to load the value from the selected SI2
load register into the SI2 counter. Related bitfields: AI_SI2_Load.
Table 2-9.
Internal Signals (Continued)
Signal
Description