I want to use PIN1  of CY8C4013SXI-400.
Hello Hayato san,
You can use that pin for the functionality. But you need to make sure that during any POR , the pin must not have a load to ground. The device will remain in XRES state in such cases, as the reset signal is always asserted. You may use some other pin for the functionality if you cannot guarantee the pin state during any of the POR on the entire device life cycle.
Are you suggesting to configure GPIO P1.6 as input mode with PSoC internal config of pull-up/down? Or, are you configuring P1.6 as an input and putting an external pull-up/down resistor on P1.6? I'm not sure of your statement.
When PSoC powers ON, it resets internally, configures internal settings and runs an internal boot process. Then, PSoC jumps to user application code. An external pull-down resistor connected to P1.6 will hold PSoC in reset state. I've never tried an internal GPIO configured pull-down resistor, so I don't know the outcome.
If both a pull-up and pull-down resistors are connected externally to P1.6, this will confuse PSoC and PSoC will sometimes interpret a logic HI or a logic LOW. Not very reliable. If GPIO is configured as pull-up/pull-down, I don't think this is reliable.
If PSoC P1.6 is configured for internal (or external) pull-up resistor, this is okay to use.
So, I don't know how you can avoid PSoC observing a pull-down resistor in the first 100ms after power ON. The application code has no hardware control during this first 100ms.
A pull-up resistor is fine. Be aware, application code would always take this branch after power ON.