- Important fact:
- A memory address is
(always) a
32 bit binary number
I.e.:
- A memory address is (always) a "large" number !!!
That means that if you need to move the memory address memAddress into a register, you must use:
movw rN, #:lower16:memAddress movt rN, #:upper16:memAddress
- A memory address is
(always) a
32 bit binary number
- Recall that
we always use
labels to
mark
important memory addresses
And the assembler has conveniently equated every label used in an assembler program to its corresponding memory address for us !!!
So if you need to move a memory address into a register, you can use its label to represent the memory address value !!!
- Example:
- Previous,
we have define
a int constant value in the
.data segment
as follows:
.data intConst: .word 4444Recall that the assembler will put the binary number in some memory location and equates that memory location with the identifier (label) intConst
Explained using a picture:
In other words: the symbolic name intConst is equal to the memory address (which is always a large number) of the memory location where that number is located.
- Suppose we want to
move the
memory address where the
integer is stored into
the register r0.
From the above discussion, we need to use the following 2 instructions:
movw r0, #:lower16:intConst movt r0, #:upper16:intConst
- Previous,
we have define
a int constant value in the
.data segment
as follows:
- Example Program:
(Demo above code)
- Prog file: /home/cs255001/demo/asm/2-mov/mov-address.s
How to run the program:
- To compile: as255 mov-address
- To run: use EGTAPI
In class, I will show you that the register r0 will indeed contain the address 100228 which is the memory location of the value 4444 in the memory.