Chapter 2
Analog Input Timing/Control
DAQ-STC Technical Reference Manual
2-128
©
National Instruments Corporation
The SI2 load signal (SI2_LOAD) enables the SI2 counter to reload from the selected load
register on the next clock. SI2_LOAD is asserted when SI2_TC is reached or is asserted by
software.
The SI2 count enable signal (SI2_CE) allows the SI2 counter to count. SI2_CE is asserted on
any transition terminating at the CNT state, provided that the SI2 counter is armed.
The SI2 disarm signal (SI2_DISARM) clears the AI_SI2_Arm bit in the register map.
SI2_DISARM is asserted on the transition from the CNT state to the WAIT1 state when
AI_End_On_End_Of_Scan, AI_End_On_SC_TC, or AI_Trigger_Once is high.
Figure 2-51.
SI2 Control Circuit State Transitions
2.8.3.7 DIV Counter
The DIV counter is a 16-bit down counter. The DIV counter typically divides down
LOCALMUX_CLK when an external multiplexer is used. The DIV counter uses the same
clock that is selected for the SC counter (SC_SRC). The counter load register is directly
accessible from the register map. If the counter is disarmed, AI_DIV_Load will load the
counter with the value from the load register. During normal operation, the DIV counter will
synchronously reload from the load register following DIV_TC. The DIV control circuit
generates the count enable signals.
(AB)'
WAIT1
WAIT2
CNT
ABF
E' + M'
F'
ABF'
F
EMT'
A
B
E
F
G
H
I
J
M
N
SI_START1
AI_SI2_Arm
SI2_TC
START
SC_TC
AI_End_On_End_Of_Scan
AI_End_On_SC_TC
AI_Continuous
STOP
AI_Trigger_Once
T = G'H' + H'I'J
SI2_LOAD = E + AI_SI2_Load
SI2_CE = AI_SI2_Arm (CNT1(n+1))
S2I_DISARM = CNT(n) WAIT1(n+1) (H + I + N)
EMT