Re: Two Ethernet MACs in a new DualCore ARM Microcontroller



Ulf Samuelsson wrote:
42Bastian Schick wrote:
On Wed, 26 Apr 2006 12:29:49 +0200, "Ulf Samuelsson"
<ulf@xxxxxxxxxxxxx> wrote:

To me the fact that a CPU is combined with peripherals makes it
a microcontroller, but this is my private opinion.
There are no clear boundaries and a discussion is probably a waste
of time.
That's I've been tought: CPU + peripherals (even ROM) =>
microcontroller. But with this definitions the AMD Opteron with RAM
interface is a microcontrollers too.

I think any definition should be rule based.
The rules below are prioritized, and once a decision is made,
there is no need to parse lower priority rules.

Rule 1) Anything running late versions of Windows (CE does not count
here) is not a microcontroller

This is a pretty arbitrary, and isn't really necessary.

I am going to ignore all comment about Geode...
Rule 2) Anything without internal code memory (cache does not count here)
is not a microcontroller

I disagree. There are plenty of microcontrollers that have no internal code memory. Consider, as an example, the MPC561, which is a microcontroller based around the PPC core. The MPC563 device is identical, except that it has on-chip flash. Does that make the MPC563 a microcontroller and the MPC561 a microprocessor? This rule would be better as "anything with internal code or data memory is a microcontroller".

Rule 3) Anything with a serial communication channel, is a
microcontroller
Rule 4) Anything without minimum 1 timer providing a periodic interrupt
is not a microcontroller
Rule 5) Anything without minimum 1 programmable I/O pin is not a
microcontroller

I'd say it is difficult to formulate an exact rule, but the main point is that if the device has on-chip peripherals, it is a microcontroller.

Rule 6) Anyting REQUIRING a companion chip, is not a microcontroller

This is fair enough. A microcontroller should either run from internal memories, or have glueless (or almost glueless) buses for external memories. You might need the occasional inverter or address latch, but you should not need external address decoding or bus control.

...
Rule n) It is a microcontroller

If I follow these rules above (which I just invented), then
the chips I can think of which I intuitively think are microcontrollers
will be classified as microcontrollers.


What's needed are a few well-known examples of borderline cases for testing the rules.

.