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General Information Chapter Four: Analog/TTL Operation
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Chapter Four: Analog/TTL Operation
General Information
Digital inputs and outputs are designed to interface with low power TTL and CMOS logic families. They also
include additional components to protect against damage from ESD or transient voltages.
Selecting the Digital Input Functions
The specific function of each digital input is listed in Table 18. To select an input function, pull the
appropriate input pin to a TTL low level (0 to 0.8 Volts) for a minimum of 50 milliseconds.
The TTL low signal is “level sensitive” meaning that once the signal is held low, the T3 unit may take up to
50 milliseconds to recognize the command. The line must be held low
continuously for the T3 unit to use the
selected parameters. Once the signal goes high, the controller will default back to the state associated with the
high signal within 50 milliseconds.
When the input is brought high (+2.4 to +5 Volts), any lower priority functions that have been selected will be
activated, even if they were previously suppressed.
Refer to Table 11, Auxiliary Connector Pin Out , on page 20 for the complete Interface connector pin out.
Table 18: Digital Input Functions
I/O Pin No. State Digital Input Function
3 Low
High
Open the valve
No function
4 Low
High
Close the valve
No function
5 Low
High
Analog set point to position
Analog set point to pressure (default)
6 Low
High
PID
Model based
7 Low
High
Learn Valve Steps
No function
8 Low
High
Learn System Conductance
No function
22 Low
High
Disable Interlock
No function
23 Low
High
Remote Zero Command
No function