e=1/0!+1/1!+1/2!+....

How to write an assembly language calculating e using ARM cortex M4?

Here is my code:

AREA PROG1,CODE,READONLY

ENTRY

MOV r6, #2 ; load 2 into register 6, cause the first two item sum up to 2, so set the sum to 2

;I know factorial Calculation will be used, but I can't figure out how to write the code(algorithm)

stop B stop

END

Please help me with the code, thank you !!