The time delay created by a timer on the ARM M4 processors is dependent on three

Question

The time delay created by a timer on the ARM M4 processors is dependent on three values: f_dk = the value of the clock frequency Arr = the number in the auto-reload register Psc = the number in the prescale register. Write a single equation which expresses the time delay in seconds in terms of these three variables. Answer the following questions about the program below: What is the value of each of these variables after the program completes? x = What is the value of each of these registers when the program completes? R0 = #include "stm32f407vg.h" asm int Mystery(int a, int b); int main() {int x, y, z; x = 3; y = 13; z = Mystery(x, y);} asm int Mystery(int a, int b) {ADO R0, R1; BX LR;} The ARM architecture supports a 32-bit instruction set and a 16-bit Thumb instruction set. Why are there two different instruction sets?

Explanation / Answer

19)A)

x=3,

y=13,

z=16

19)B)

R0=3

R1=13

20)answer:

1)It is stated that all ARM instructions are 32 bits long. Instructions are stored in to theword-aligned, so the least most significant two bits of instruction addresses are always zero in ARM state.

2)Thumb instructions are either 16 or 32 bits long. Instructions are stored into the half-word aligned. Some instructions use the least one of the significant bit of the address to be set to whether determine the code being branched to is Thumb code or ARM code.

3)Before the introduction of 32-bit Thumb instructions, the Thumb instruction set was designed the limited to a restricted subset of the functionality of the ARM instruction set. Almost all Thumb instructions were follows the 16-bit. Together, the 32-bit and 16-bit Thumb instructions provide functionality that is almost identical to that of the ARM instruction set.

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