When a device interrupt occurs, how does the processor determine which device issued the interrupt|My homework helper

Assignment Content

1. Question 1

In virtually all systems that include DMA modules, DMA to main memory is given higher priority than CPU access to main memory. Why? 

Question 2

When a device interrupt occurs, how does the processor determine which device issued the interrupt? 

Question 3

A system is based on an 8-bit microprocessor and has two I/O devices. 

• The I/O con- trollers for this system use separate control and status registers.
• Both devices handle data on a 1-byte-at-a-time basis.
• The first device has two status lines and three control lines.
• The second device has three status lines and four control lines.
• How many 8-bit I/O control module registers do we need for status reading and control of each device? 

  ***Explain your reasoning and show your mathematical calculations on how you derived your answer 

• Question 4

  A system is based on an 8-bit microprocessor and has two I/O devices. 

• The I/O con- trollers for this system use separate control and status registers. 
• Both devices handle data on a 1-byte-at-a-time basis. 
• The first device has two status lines and three control lines. 
• The second device has three status lines and four control lines. 
• What is the total number of needed control module registers given that the first device is an output-only device? 

  ***Explain your reasoning and show your mathematical calculations on how you derived your answer 

• Question 5

  A system is based on an 8-bit microprocessor and has two I/O devices. 

• The I/O con- trollers for this system use separate control and status registers. 
• Both devices handle data on a 1-byte-at-a-time basis. 
• The first device has two status lines and three control lines. 
• The second device has three status lines and four control lines. 
• How many distinct addresses are needed to control the two devices? 

  ***Explain your reasoning and show your mathematical calculations on how you derived your answer 

• Question 6

  Consider a microprocessor that has a block I/O transfer instruction such as that found on the Z8000. 

• Following its first execution, such an instruction takes five clock cycles to re-execute.
•  However, if we employ a nonblocking I/O instruction, it takes a total of 20 clock cycles for fetching and execution.
• Calculate the increase in speed with the block I/O instruction when transferring blocks of 128 bytes. 

  **Explain your reasoning and show your mathematical calculations on how you derived your answer 

• Question 7
• What is the difference between memory-mapped I/O and isolated I/O? 

SOLUTION

This is generally true because DMA allows for faster transfer of data between peripheral devices and main memory, which can improve overall system performance. Giving DMA higher priority ensures that these data transfers are completed quickly and efficiently, while also minimizing the amount of time that the CPU is blocked from accessing main memory.

However, it is worth noting that some systems may have different priority schemes or use different methods for managing DMA and CPU access to main memory depending on the specific system design and requirements.