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Denser, smaller, better 8bit devices emerge

Posted: 16 Mar 2005     Print Version  Bookmark and Share


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By Lucio Di Jasio

Product Marketing Manager

Advanced Microcontroller

Architectures Division

Microchip Technology Inc.

Although we use powerful,

multigigahertz 32bit and 64bit

processors inside our PDAs,

desktop PCs and workstations,

we are surrounded everyday by

other products that, at their


8bit MCUs. These MCUs repre-

sent the majority of intelligent

non-life forms that surround us.

One reason for the 8bit

MCU's long and successful life

is its great adaptability. The

migration from ROM and one-


flash technology has enabled

new categories of applications

where designers can quickly

adapt their products to the de-

mands of a market that expects


smarter products.

With the introduction of de-

vices in smaller packages,

which are down to eight-pin

and now six-pin SOT-23 pack-

ages, the last barriers have col-

lapsed. Potentially packing up


integrated 4MHz oscillator, an

8bit timer, an analog compara-

tor and four GPIOs, these six-

pin devices are far more inte-

grated and flexible than any

4bit MCU.

One of the staunchest barri-

ers to the growth of 8bit appli-

cations that used to force many

designers to develop with 16bit

and 32bit processors was rela-

tively demolished when 8bit ar-

chitectures with program-

memory sizes larger than 64KB

were introduced.

The amount of memory an

MCU can address is dictated by

the size of the address bus. For


tive 8bit architectures had their

address buses set to twice the

data-bus size or 16bits. These

8bit architectures created what

seemed like an insurmountable

barrier at 64KB. Beyond that

barrier, things were quickly be-

Denser, smaller, better 8bit

devices emerge




facturers have introduced 8-bit-

ters that can address up to sev-

eral megabytes of program


The ultimate example of the

8bit MCU's evolution can per-

haps be found by looking at one

of the most advanced embed-

ded applications--Ethernet. As

with many other complex pro-

tocols, the TCP/IP stack that is

the foundation of all Ethernet

Source: Microchip Technology

Application + data







Front-desk hub


Applications that once needed a 32bit MCU can now be serviced by

today's more-powerful 8bit MCUs with onboard TCP/IP stacks.

applications was developed in

the mainframe world and was

later adapted to workstations

and PCs, where mostly 32bit

and 64bit processors were be-

ing used. Porting the code and

compacting it to fit in an 8bit

MCU's onboard memory might

have seemed quite a challenge

at one time. But today, free

TCP/IP software stacks are


turers that fit comfortably in

the roomy flash memory of the

most capable 8bit devices.



cost applications while offering

capabilities that open new hori-


with very low power consump-

tion are possible through the

sophisticated power manage-


modern 8bit architectures.


ogy, available on most recent

PIC MCUs, is one example. The

nanoWatt Technology offers up

to seven low-power modes and

helps designers modulate per-

formance with long battery life

and robustness.

Embedded 8bit MCUs are

often called on to perform in

harsh and unforgiving environ-

ments. Onboard watchdog cir-

cuits based on independent os-

cillators, fail-safe clock moni-

tors and brownout and low-

voltage detect circuits com-

plete the standard toolset and

can make the modern 8bit

MCU a good alternative to

larger architectures in many

demanding applications.

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