Engineering Questions with Answers - Multiple Choice Questions

MCQs on Programmable DMA Interface 8237 -1

1 - Question

The block of 8237 that decodes the various commands given to the 8237 by the CPU is
a) timing and control block
b) program command control block
c) priority block
d) none of the mentioned

View Answer

Answer: b
Explanation: The program control block decodes various commands given to the 8237 by the CPU before servicing a DMA request.




2 - Question

The priority between the DMA channels requesting the services can be resolved by
a) timing and control block
b) program command control block
c) priority block
d) none of the mentioned

View Answer

Answer: c
Explanation: The priority encoder block resolves the priority between the DMA channels requesting the services.




3 - Question

The register that holds the current memory address is
a) current word register
b) current address register
c) base address register
d) command register

View Answer

Answer: b
Explanation: The current address register holds the current memory address. The current address register is accessed during the DMA transfer.




4 - Question

The register that holds the data byte transfers to be carried out is
a) current word register
b) current address register
c) base address register
d) command register

View Answer

Answer: a
Explanation: The current word register is a 16-bit register that holds the data transfers. The word count is decremented after each transfer, and the new value is stored again in the register.




5 - Question

When the count becomes zero in the current word register then
a) Input signal is enabled
b) Output signal is enabled
c) EOP (end of process) is generated
d) Start of process is generated

View Answer

Answer: c
Explanation: When the count becomes zero, the EOP signal is generated. This can be written in successive bytes by the CPU, in program mode.




6 - Question

The current address register is programmed by the CPU as
a) bit-wise
b) byte-wise
c) bit-wise and byte-wise
d) none of the mentioned

View Answer

Answer: b
Explanation: The current address register is byte-wise programmed by the CPU, i.e. lower byte first and the higher byte later.




7 - Question

Which of these register’s contents is used for auto-initialization (internally)?
a) current word register
b) current address register
c) base address register
d) command register

View Answer

Answer: c
Explanation: The contents of base address register cannot be read by the CPU. These contents are used internally for auto-initialization.




8 - Question

The register that maintains an original copy of the respective initial current address register and current word register is
a) mode register
b) base address register
c) command register
d) mask register

View Answer

Answer: b
Explanation: The base address register maintains an original copy of the current address register and current word register, before incrementing or decrementing.




9 - Question

The register that can be automatically incremented or decremented, after each DMA transfer is
a) mask register
b) mode register
c) command register
d) current address register

View Answer

Answer: d
Explanation: The address is automatically incremented or decremented after each DMA transfer, and the resulting address value is again stored in the current address register.




10 - Question

Which of the following is a type of DMA transfer?
a) memory read
b) memory write
c) verify transfer
d) all of the mentioned

View Answer

Answer: d
Explanation: Memory read, memory write and verify transfer are the three types of DMA transfer.

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