28.5.3 Clocks
The PORT bus clock (CLK_PORT_APB) can be enabled and disabled in the Main Clock module, and the default state of CLK_PORT_APB can be found in the Peripheral Clock Masking section in the MCLK - Main Clock.
The PORT is fed by two different clocks: a CPU main clock, which allows the CPU to access the PORT through the low latency CPU local bus (IOBUS); an APB clock, which is a divided clock of the CPU main clock and allows the CPU to access the registers of PORT through the high-speed matrix and the AHB/APB bridge.
The priority of IOBUS accesses is higher than event accesses and APB accesses. The EVSYS and APB will insert wait states in the event of concurrent PORT accesses.
The PORT input synchronizers use the CPU main clock so that the resynchronization delay is minimized with respect to the APB clock.
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