Knowledge Base Article
Immediately after the POR event, all the GPIO pins except P1[0] and P1[1] are in High Impedance state. They remain in this state till they are reconfigured according to project settings in the psocconfigtbl.asm file.
At power up, the internal POR causes P1[0] to initially drive a strong high (1) while P1[1] drives a resistive low (0). After 256 sleep oscillator cycles (approximately 8 ms), the P1[0] signal transitions to a resistive low state. After additional 256 sleep oscillator clocks, both pins transition to a high impedance state and normal CPU operation begins.
More details with timing diagrams may be found in the Technical Reference Manual Section 30 >> System Resets >> GPIO Behavior During Reset
This applies to the following families of PSoC:
CY8CPLC20, CY8CLED16P01, CY8C29x66,CY8C27x43, CY8C24x94, CY8C24x23, CY8C24x23A,CY8C22x13, CY8C21x34, CY8C21x23,CY7C64215, CY7C603xx, CY8CNP1xx, and CYWUSB6953