What is Input / Output Structure?
I/O Module
BSCSF15MM05
BSCSF15MM32
BSCSF15MM46
Input/Output Module
• Interface to CPU and Memory
• Interface to one or more peripherals
• Unique addresses for every device in memory if more
than one device than more than one addresses.
External Devices
• Human readable (human interface)
• Monitor, printer, keyboard, mouse
• Machine readable
• Disk, tape, sensors
• Communication
• Modem
• Network Interface Card (NIC)
I/O Module Function
• Control & Timing
• CPU (Processor) Communication
• Device Communication
• Data Buffering
• Error Detection (e.g., extra parity bit)
I/O Steps
• CPU checks (interrogates) I/O module device status
• I/O module returns status
• If ready, CPU requests data transfer by sending a
command to the I/O module
• I/O module gets a unit of data (byte, word, etc.)
from device
• I/O module transfers data to CPU
Input/Output Problems
• Wide variety of input output devices
• Delivering different amounts of data
• At different speeds
• In different formats
• All slower than CPU and RAM
• Need I/O modules w/ some “intelligence”
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