Using external crystal in PSoC1 dvices

Connect a 32.768 KHz crystal with two 10 pF bias capacitors to pins port1_0 and port1_1. In the PSoC Designer Device Editor configure the crystal pins for the High Z state. In the global resources window of the Device Editor enable the 32K_Select option. The external crystal source is now available as the CPU_32_KHz clock source. By enabling PLL_Mode in global resources, all internal clocks are derived from the external crystal.

For more information see the application note,  AN2027 - Using the PSoC Microcontroller External Crystal Oscillator