Embedded Systems Design, 2nd Edition

Memory and performance trade-offs 363

case timing has to be assumed, even though statistically the

routine will execute faster 99.999% of the time!

Using on-chip memory

Some microcontrollers and DSP chips have local memory

which can be used to store data or instructions and thus offers fast

local storage. Any access to it will be fast and thus data and code

structures will always gain some benefit if they are located here.

The problem is that to gain the best benefit, both the code and data

structures must fit in the on-chip memory so that no external

accesses are necessary. This may not be possible for some pro-

grams and therefore decisions have to be ...