Question

Assume SP = 0x20001010 before the following instructions are executed:

MOV R0, #0

MOV R1, #1

MOV R2, #2

PUSH {R0, R1, R2}

After these instructions execute:

What is the value of the SP? _________________

What is the value of the following memory locations (place X in the blank if it cannot be calculated):

Address 32-bit Data

0x2000101C ____________

0x20001018 ____________

0x20001014 ____________

0x20001010 ____________

0x2000100C ____________

0x20001008 ____________

0x20001004 ____________

0x20001000 ____________

Answer 1

The stack pointer stores the address of the most recent entry that was pushed onto the stack.The push instruction first subtracts and then inserts the data.
SP = 0x20001010
MOV R0, #0 //R0<-0
MOV R1, #1 //R1<-1
MOV R2, #2 //R2<-2

PUSH {R0, R1, R2}
Here three push
SP = SP-4
0x20001010 - 4 = 0x2000100C
then push data at 0x2000100C = R0
SP = SP-4
0x2000100C - 4 = 0x20001008
then push data at 0x20001008 = R1
SP = SP-4
0x20001008 - 4 = 0x20001004
then push data at 0x20001004 = R2

The value of the SP = 0x20001004

Address 32-bit Data

0x2000101C ______X______

0x20001018 ______X______

0x20001014 ______X______

0x20001010 ______X______

0x2000100C ______0______

0x20001008 ______1______

0x20001004 ______2______

0x20001000 ______X______