MGMT 1040 Chapter Notes - Chapter 20: Floppy Disk
8 May 2018
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MGMT 1040 Chapter 20 Notes – Summary
Introduction
• Peripherals such as printers and floppy disk drives can convey emergency status
information to the executing program.
• Programmed I/O is suitable only for slow devices and individual word transfers.
• For faster devices with block transfers, there must be a more efficient means of
transferring the data between I/O and memory.
• Memory is a suitable medium for direct block transfers
• Since the data has to be in memory for a program to access it.
• Preferably this could be done without involving the CPU, since this would free the CPU
to work on other tasks.
• The buses that interconnect high-speed I/O devices with the computer must be capable
of the high data transfer rates characteristic of modern systems.
• Finally, there must be a means for handling devices with extremely different control
requirements.
• It would be desirable if I/O for each of these devices could be handled in a simple and
similar way by programs in the CPU.
• The last requirement suggests that it is not practical to connect the I/O devices directly
to the CPU without some sort of interface module unique to each device.
• To clarify this requirement, note the conditions established from the previous discussion
• The formats required by different devices will be different.
• Some devices require a single piece of data, and then must wait before another piece of
data can be accepted.
• Others expect a block of data.
• Some devices expect 8 bits of data at a time
• Others require 16, 32, or 64.
• Some devices expect the data to be provided sequentially, on a single data line.
• Other devices expect a parallel interface.
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