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AmpConnect 621
™
Manual Digital I/O Operation 33
TTL Input Example
SoundCheck may also need to receive a TTL signal from
an external device such as a Production Line Controller.

Figure 7-14 shows the output of such a device
connected across Bit 5 and Ret. (GND)

A pull down resistor is added between Bit 5 and
Ret. (GND). The resistor value is dependent on
the level of the TTL signal.

The max level allowed for the TTL signal is
+5 VDC tolerant. Turn on voltage is
+2 VDC nominal. Max turn off voltage is 0.8 VDC.

When the Production Line Controller sends a
+3 VDC signal to Bit line 5, it will pull the bit High

The max output TTL signal is +3.3 VDC
When the Digital I/O Message Step is executed in the sequence, it will
Read the actual state of the input and compare it to the Message Step
setting of Bit 5 shown in
Figure 7-15 .

Bit 5 is set Low as the “normal” mode for the step so that it will
react to the Bit being pulled High by the ex3.3 VDC
signal

The Pass/Fail radio buttons are not used

If the actual state of the input agrees with the setting for Bit 5
the step will issue a "PASS" verdict

If the actual state disagrees the step will issue a "FAIL" verdict.
This “FAIL” will be used in the Step Configuration shown in
Figure
7-16 .

Right click on a step in the Sequence Editor to select
“Configure Step”

In this case, the “FAIL” verdict is used to tell the step to jump to a
failure message, “Bit 5 Failed”.
Digital I/O Port
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
+3.3V
Ret. (GND)
TTL Signal
Production Line
Controller
+
x Ohm
Pull Down
Resistor
Figure 7-14: Bit 5 - Normal Logic Input
Figure 7-15: Bit 5 Set High
Figure 7-16: Jump On
Fail