Hardware Devices
Question 1 |
Of the following, which best characterizes computers that use memory-mapped I/O?
The computer provides special instructions for manipulating I/O ports | |
I/O ports are placed at addresses on the bus and are accessed just like other memory locations | |
To perform I/O operations, it is sufficient to place the data in an address register and call channel to perform the operation | |
I/O can be performed only when memory management hardware is turned on |
Question 1 Explanation:
→ Memory-mapped I/O uses the same address space to address both memory and I/O devices.
→ The memory and registers of the I/O devices are mapped to (associated with) address values.
→ So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to the memory of the I/O device. Thus, the CPU instructions used to access the memory can also be used for accessing devices.
→ Each I/O device monitors the CPU's address bus and responds to any CPU access of an address assigned to that device, connecting the data bus to the desired device's hardware register.
→ To accommodate the I/O devices, areas of the addresses used by the CPU must be reserved for I/O and must not be available for normal physical memory.
→ The reservation may be permanent, or temporary (as achieved via bank switching).
→ The memory and registers of the I/O devices are mapped to (associated with) address values.
→ So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to the memory of the I/O device. Thus, the CPU instructions used to access the memory can also be used for accessing devices.
→ Each I/O device monitors the CPU's address bus and responds to any CPU access of an address assigned to that device, connecting the data bus to the desired device's hardware register.
→ To accommodate the I/O devices, areas of the addresses used by the CPU must be reserved for I/O and must not be available for normal physical memory.
→ The reservation may be permanent, or temporary (as achieved via bank switching).
Question 2 |
In a microcomputer, WAIT states are used to
make the processor wait during a DMA operation | |
make the processor wait during a power interrupt processing | |
make the processor wait during a power shutdown | |
interface slow peripherals to the processor |
Question 2 Explanation:
● A wait state is a situation in which a computer program or processor is waiting for the completion of some event before resuming activity. A program or process in a wait state is inactive for the duration of the wait state.
● A wait state is a delay experienced by a computer processor when accessing external memory or another device that is slow to respond.
● A wait state is a delay experienced by a computer processor when accessing external memory or another device that is slow to respond.
There are 2 questions to complete.