Chapter 2
Analog Input Timing/Control
©
National Instruments Corporation
2-125
DAQ-STC Technical Reference Manual
The SC load signal (SC_LOAD) enables the SC counter to reload from the selected load
register on the next clock. SC_LOAD asserts when SC_TC is reached and TRANS is high or
it is asserted by software (AI_SC_Load).
The SC count enable signal (SC_CE) allows the SI counter to count. SC_CE asserts on any
transition originating from or terminating at either of the PCNT or CNT states, provided that
the SC counter is armed (AI_SC_Arm), TRANS is high, and EXT_GATE is enabled.
The SC disarm signal (SC_DISARM) clears the AI_SC_Arm bit in the register map.
SC_DISARM asserts on the transition from the CNT state to the WAIT1 state when either
AI_End_On_End_Of_Scan, AI_End_On_SC_TC, or AI_Trigger_Once is high.
Figure 2-49.
SC Control Circuit State Transitions
(AB)'
WAIT1
PCNT
WAIT2
CNT
(GL)'
ABK'
L' + T
F'
GL
F
ABK
LT'
A
B
F
G
H
I
J
K
L
N
T
SC_START1
AI_SC_Arm
START2
SC_TC
AI_End_On_End_Of_Scan
AI_End_On_SC_TC
AI_Continuous
AI_Pre_Trigger
TRANS
AI_Trigger_Once
G'H' + H'I'J
SCKG = AI_CONVERT_Source_ SI2_TC
TRANS = SCKG (STOP)
SC_LOAD = GL + AI_SC_Load
SC_CE = BL (EXT_GATE) (PCNT(n) + CNT(n) + PCNT(n+1) + CNT(n+1))
SC_DISARM = CNT(n) WAIT(n+1) (H + I + N)