MKS 651D Series, User Manual, Page: 126 / 162

How To Select the Digital Input Functions Chapter Six: Remote Digital Logic Control
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Digital Input Priorities
Digital inputs are scanned and selected in a prioritized manner, enabling a higher priority request
to override a lower one. The order of priority is shown in Table 18.
Priority of Digital Inputs
Order of Priority I/O Pin No. Digital Input Function
1 6 Analog set point
(pressure or position)
2 10 Control range of analog set point
Note: Below this point, if any of the digital inputs are held low, lower priority
signals are blocked; that is, they are not recognized until the higher priority
signal is released.
3 25 Remote zero
4 5 No function
5 8 Close valve
6 27 Open valve*
7 26 Stop valve*
8 11 Select analog set point
9 16 Select set point A
10 15 Select set point B
11 14 Select set point C
12 13 Select set point D
13 12 Select set point E
* Activating both the open and close commands simultaneously causes the
valve to stop .
Table 18: Priority of Digital Inputs
The order of priority of digital inputs is based on the analog set point line (pin 11) being tied low
to continuously select it, thus blocking set points A through E, except to use their gains.