I/o devices | Computer Science homework help
Assignment Content
- 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?
