7. Computer Function
• Program Counter
• Contains the address of the next Instruction
• Instruction Register
• Contains the address of the current instruction
• Memory Buffer Register (MBR)
• contains the data to be written into memory or receives the data
read from memory.
• Memory Address Register (MAR)
• specifies the address in memory for the next read or write
8. Computer Function
• I/O Address register
• specifies a particular I/O device
• IO Buffer register
• is used for the exchange of data between an I/O module and the
CPU.
• Memory Module
• consists of a set of locations, defined by sequentially numbered
addresses.
• IO Module
• An I/O module transfers data from external devices to CPU and
memory, and vice versa. It contains internal buffers for temporarily
holding these data until they can be sent on..
9. Computer Function
• Processor-memory
• Data may be transferred from processor to memory or from memory to
processor.
• Processor-I/O
• Data may be transferred to or from a peripheral device by transferring
between the processor and an I/O module.
• Data processing
• The processor may perform some arithmetic or logic operation on
data.
• Control
• An instruction may specify that the sequence of execution be altered.
For example, the processor may fetch an instruction from location 149,
which specifies that the next instruction be from location 182. The
processor will remember this fact by setting the program counter to
182.Thus, on the next fetch cycle, the instruction will be fetched from
location 182 rather than 150.
11. Tuesday, March 06, 2012 PRADEEP KUMAR TS 11
Instruction Fetch and Execute
12. Tuesday, March 06, 2012 PRADEEP KUMAR TS 12
Instruction Fetch and Execute
13. Tuesday, March 06, 2012 PRADEEP KUMAR TS 13
Interrupts and their effects
• Classes of Interrupts
• Program
• Generated by some condition that occurs as a result of an instruction
execution, such as arithmetic overflow, division by zero, attempt to
execute an illegal machine instruction,
• Timer
Interrupts generated by the OS to take some special actions
• I/O
• Generated by the I/O Controllers like signals, errors, etc
• Hardware Failure
• Power failure or memory parity error
14. Tuesday, March 06, 2012 PRADEEP KUMAR TS 14
Interrupts and Instruction Cycle
15. Tuesday, March 06, 2012 PRADEEP KUMAR TS 15
Interrupts and Instruction Cycle
16. Tuesday, March 06, 2012 PRADEEP KUMAR TS 16
Interrupts and Instruction Cycle
