Rev. 1.0
111
Si4010-C2
30.1. GPIO Pin Special Roles
Not all GPIO ports can be configured as both input and outputs. Given the limited number of GPIO each
pin can assume different functionality based on the software configuration of the ports. The functionality of
each GPIO is described in Table 30.3.
It is important to emphasize the following:
GPIO[0] can be used only as input for user application. It can also serve as a crystal oscillator input.
During device NVM programming the programming VPP=6.5V voltage is applied to this pin.
GPIO[5] can be used only as a up to 1mA LED current driver. The LED should be connected directly in
between the GPIO[5] and VCC. In a development system this pin is used as a C2 interface C2CLK. In
the development system the LED has to be isolated from the pin as shown in Figure 35.1 and
Figure 35.2. The LED is disabled during debugging.
Table 30.3. GPIO Special Roles
GPIO Number
Other Special Roles
C2
FOB
Can Drive
Low During
Sleep
Pullup Roff
Option
0
XO/VPP1
button
1
button
Y
Y
2
button
Y
Y
3
clk_ref
button
Y
4
clk_out out
C2DAT
button
5
C2CLK
LED
6 (14 pin only)
clk_out out
button
7 (14 pin only)
button
8 (14 pin only)
button
9 (14 pin only)
button
Notes:
1.
Can be set as GPIO input only. Special roles are crystal oscillator (XO) and VPP=6.5V NVM
programming voltage supply during NVM programming.
2.
Reference clock source for frequency counter.
3.
Current mode driver for LED connected directly to VCC supply. GPIO[5] cannot be used for any
other purpose in user application.
4.
Optional customer clock
clk_out
output can be set independently on GPIO[4] and GPIO[6], or on
both at the same time.