Chapter 2
Analog Input Timing/Control
DAQ-STC Technical Reference Manual
2-56
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National Instruments Corporation
AI_External_MUX_Present
bit: 12
type: Write
in: AI_Mode_2_Register
address: 13
This bit determines when the LOCALMUX_CLK output signal pulses:
0: Pulse on every CONVERT.
1: Pulse only on CONVERTs that occur during DIV_TC.
This bit allows you to use the DIV counter for LOCALMUX_CLK signal control. This is
useful if one or more external multiplexers, such as an AMUX-64T or SCXI, are connected
to the board the DAQ-STC is on. You should set this bit to 0 if no external multiplexers are
present or if each external channel corresponds to one internal channel. You should set this
bit to 1 if one or more external multiplexers are present and if you are multiplexing more than
one external channel onto each internal channel. If this bit is set to 1, the DIV counter must
be used to determine the number of EXTMUX_CLK pulses that will correspond to one
LOCALMUX_CLK pulse.
AI_EXTMUX_CLK_Output_Select
bits: <6..7>
type: Write
in: AI_Output_Control_Register
address: 60
This bit enables and selects polarity for the EXTMUX_CLK output signal:
0: High Z.
1: Ground.
2: Enable, active low.
3: Enable, active high.
AI_EXTMUX_CLK_Pulse
bit: 3
type: Strobe
in: AI_Command_1_Register
address: 8
Setting this bit to 1 produces a pulse on the EXTMUX_CLK output signal if the output is
enabled. The pulsewidth is determined by AI_EXTMUX_CLK_Pulse_Width. This bit is
cleared automatically. Related bitfields: AI_EXTMUX_CLK_Output_Select,
AI_EXTMUX_CLK_Pulse_Width.
AI_EXTMUX_CLK_Pulse_Width
bit: 6
type: Write
in: AI_Personal_Register
address: 77
This bit selects the pulsewidth and assertion time of the EXTMUX_CLK output signal:
0: Pulsewidth is 4.5 AI_OUT_TIMEBASE periods. EXTMUX_CLK trails the
LOCALMUX_CLK pulse by 0.5–1.5 AI_OUT_TIMEBASE periods.
1: Pulsewidth is equal to the pulsewidth of the LOCALMUX_CLK read pulse selected
by AI_LOCALMUX_CLK_Pulse_Width. EXTMUX_CLK and
LOCALMUX_CLK are asserted at the same time.
Related bitfields: AI_LOCALMUX_CLK_Pulse_Width.