Computer knowledge

Direct Access Memory  Port and Memory-Mapped I/O: As stated earlier, the CPU communicates with the I/O controller or module to perform any input/output operating. Each controller has one or two registers that are used for communicating with the CPU. The CPU communicates with the controller by reading or writing bit patterns in these registers. The CPU can access the I/O modules by using one of the following.  I/O Port  Memory-Mapped I/O  I/O Port:  With the I/O port, the communication takes place between the CPU and the I/O module through the I/O port using special I/O instruction. The I/O address (or number) is given as a parameter to the I/O instruction. The I/O instruction trigger bus lines to select the proper device and its I/O ports and then moves bits into or out of a device register. Memory-Mapped I/O: Another way for communication between the CPU and the device controller is using memory-mapped I/O Each controller has a few registers that are used for c...