Embedded Systems: An Integrated Approach by Pearson

370 EMBEDDED SYSTEMS

ii)  ere are two numbers, X and Y, whose squares are to be found. Calling the pro-

cedure amounts to just writing the instruction BL SQUARE.  is instruction will

cause a branching to the procedure named SQUARE. It also copies the current PC

value to the link register (LR).

iii)  e procedure has only two instructions: one to perform squaring, and the other to

copy the LR content back to PC.  e second instruction causes a return to the main

program.

iv) We need two multiplications, in addition to the squaring operation.  ese two, that

is, 3X

2

and 5Y

2

are achieved by shifting and adding.  e MUL instruction is used as

little as possible because it takes more time, and causes higher power dissipation.

v) 