What is the role of the address decoder in an interface module?

Recognises its own address so only that interface responds

Which is NOT inside an interface module according to the answer?

Data format and speed conversion logic

2067 Asar (old course) · 4 marks

I/O bus and interface modules

Short answer

The I/O bus carries data, address, and control lines linking the CPU to interfaces. Each interface module decodes its unique address, enabling only the addressed device to respond, and contains registers for control, status, and data transfers, also handling format and speed conversion.

Explain the I/O bus and interface modules.

The I/O bus connects the CPU to all peripheral interfaces. It consists of data lines, address lines and control lines (read, write, etc.). The CPU puts a device address on the address lines; each interface module has an address decoder which recognises its own address, and only that interface is enabled to respond. Other interfaces stay disconnected from the bus.

   CPU --+----------------------------- I/O bus
         | data | address | control
     +---+---+  +---+---+  +---+---+
     |Interf.|  |Interf.|  |Interf.|
     |  1    |  |  2    |  |  3    |
     +---+---+  +---+---+  +---+---+
         |          |          |
     Keyboard    Printer      Disk

An interface module sits between the bus and the peripheral. It contains a decoder for the address, data and control/status registers (ports), and logic that converts the data format, adjusts the speed and passes commands to the device. The CPU controls the device by reading and writing the interface's registers using I/O commands (control, status, data input, data output).

✓ Answer checked by Claude Opus 5.5 (high effort)

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