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Reference Guide
Refer to the following table for the pin description of the GPIOs.
Table 3.
GPIO Pin Description
Pin #
Signal
1
GPIO25/INT 1
2
GPIO35
3
Vref
Note:
It is recommended to use a 6-wire cable accessory for easy access to these three lines. Please
refer to the Getting Started Guide at
the 6-wire cable accessory.
When the voltage reference, Vref, is not connected, if one of the GPIO output is in High state while
the other is in Low state, the GPIO in high level voltage will be at 2.3V.To avoid this voltage drop, it
is recommended to use Vref to the desired output voltage.
With Vref connected to 2.8V, both GPIO35 and GPIO25 may be interfaced with a
component that complies with the following levels.
Table 4.
GPIO Pin Operating Conditions when Vref is at 2.8V
Parameter
Mininum
V
IL
V
1.96V
IH
V
OL
V
2.8*
OH
*
Value without external load.
Figure 6.
Equivalent Circuit of V
I/O
I/O Voltage
I/O
Vref
I/O
Vref
I
2.8V ~ 15V
http://www.usr.com/support/3500
Typical
Maximum
0.84V
0.4*
, Vref = 2.8V
IL
Rev 1.0
Description
General purpose input/output or Interrupt
General purpose input/output
Voltage reference for the GPIOs
for more information about
Condition
Please refer to Figure 6.
Please refer to Figure 7.
Please refer to Figure 8.
modem Zout = 100K Pull-up to Vref, please
refer to Figure 9.
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Interfaces
17
17
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