P1 (configurable XRES) is an optional XRES pin which either can be configured as XRES or GPIO. When configured as XRES, this pin is equally good as dedicated XRES pin. Parts which have dedicated XRES pin, can use configurable XRES to simplify the board routing if needed.
This optional XRES is mainly helpful in low pin count packages (i.e. 48 pin packages) which do not have a dedicated XRES pin and this optional XRES pin can be used to reset the device. This optional XRES can be enabled in Design Wide Resources file under Systems Tab as shown in the figure below:
1. Excessive re-programming of this setting will cause unexpected results.
2. If a 48 pin package Part is programmed with unchecked "Optional XRES" in the project, then that part can't be reprogrammed. Because programming PSoC 3/5 parts over "Power Cycle" mode is currently not supported.