The navigation computer on a research boat receives position readings from a GPS receiver. It fetches an instruction from memory, decodes it, then executes ...
Question 1 Report
The navigation computer on a research boat receives position readings from a GPS receiver. It fetches an instruction from memory, decodes it, then executes it to update the displayed route. The next instruction address is held by the program counter.
(a) State what is meant by an instruction. [1]
(b) Give the role of the memory address register during the fetch stage. [2]
(c) State the role of the memory data register when an instruction is read from memory. [1]
(d) Give two reasons why the program counter must be updated during normal sequential execution. [2]
Answer Details
(a) An instruction is a command that tells the processor what operation to perform. [1 mark]
(b) During fetch, the memory address register holds the address to be accessed [1] and sends that address to memory via the address bus [1]. [2 marks]
(c) When an instruction is read from memory, the memory data register holds the instruction or data being transferred. [1 mark]
(d) The program counter is incremented [1] so it identifies the address of the following instruction [1]. This lets the CPU continue through instructions in normal sequential order. [2 marks]
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