33.5.1 Clocks
An AHB clock (CLK_CAN_AHB) is required to clock the CAN. This clock can be configured in the Main Clock peripheral (MCLK) before using the CAN.
A generic clock (GCLK_CAN) is required to clock the CAN. This clock must be configured and enabled in the GCLK- Generic Clock Controller before using the CAN.