Real-time systems require the ability to control, read, and write data to hardware devices. The wRTOS port I/O programming interfaces allow data movement in the I/O space of a processor by a user process without switching to a kernel-mode code. This functionality eliminates the need to create a device driver for every device that must be accessed. Additionally, it eliminates the latencies associated with requesting device driver services for every device access.
Port I/O provides an alternate method of communicating directly with hardware. The I/O address space is a feature on Intel® processors where each address represents an 8-bit "port." Each port typically corresponds to an 8-bit control register on a hardware device. While sequential addresses can represent the bytes in a multi-byte port, hardware designers usually employ designs with a single-byte port, and multi-byte values are entered as sequential single-byte writes to the port address. You should consult its programming reference documentation for details about a particular device.
Topics:
