Page 172 - DCAP403_Operating System

Unit 9: I/O & Secondary Storage Structure

Figure 9.14: Speaker Notes

Video card: Also known as a graphics card, video card, video board, or a video controller, a video
adapter is an internal circuit board that allows a display device, such as a monitor, to display
images from the computer.
Figure 9.15: Video Card

Task Discuss about any four I/O hardware devices.

9.3 Application I/O Interface

The I/O and memory interface are the counterparts to the bus control logic. What goes between
the bus control logic and interface is simply the conductors in the bus; therefore, the interface
must be designed to accept and send signals that are compatible with the bus control logic and its
timing. Although there are similarities in I/O interfaces, there are also signifi cant differences.
An I/O interface must be able to:
1. Interpret the address and memory-I/O select signals to determine whether or not it is
being referenced and, if so, determine which of its registers is being accessed.
2. Determine whether an input or output is being conducted and accept output data or control
information from the bus or place input data or status information on the bus.

3. Input data from or output data to the associated I/O device and convert the data from
parallel to the format acceptable to the I/O device, or vice versa.
4. Send a ready signal when data have been accepted from or placed on the data bus, thus
informing the processor that a transfer has been completed.
5. Send interrupt requests and, if there is no interrupt priority management in the bus control
logic, receive interrupt acknowledgments and send an interrupt type.
6. Receive a reset signal and reinitialize itself and, perhaps, its associated device.

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