/* Unregisters a callback. 
Unregisters a callback function, which is implemented by the user. */
void usart_unregister_callback(struct usart_module *const module, enum usart_callback callback_type)
/* Unregisters a callback. 
Unregisters a callback function, which is implemented by the user. */
void usart_unregister_callback(struct usart_module *const module, enum usart_callback callback_type)
{
	Assert(module);
	module->callback[callback_type] = NULL;
	module->callback_reg_mask &= ~(1 << callback_type);
}