Language-specific CPUs was Re: uIEC/SD == AWESOME!

Chuck Guzis cclist at sydex.com
Fri Jan 2 02:15:42 CST 2009


On 2 Jan 2009 at 8:29, Jochen Kunz wrote:

> On Thu, 1 Jan 2009 12:45:43 -0200
> "Alexandre Souza" <alexandre-listas at e-secure.com.br> wrote:
> 
> >     AVR microcontrollers are said optimized for C, but there is an
> > excellent assembler, the AVR Studio.
> They are "optimized for C" in the sense that there architecture makes
> it easy to implement C. (Flat memory, lots of registers, stack ...) I
> did a project in AVR assembler. AVRs are much easier to assembler code
> then the i8051. (The i8051 is a braindead, awkward POS. A typical intel
> design... I used it once and will never again.) Today I do all my uC
> hacking with avr-gcc. The oposit may be the PIC. Due to the PIC
> architecture a C implementation is a bit tricky.

Perhaps compared to an 8051, and a PIC, but literal constants in 
program memory have their own addressing problems (LPM uses twice the 
program space address and is the only access to program memory).  
Since SP is in I/O space and not register space, it takes extra 
instructions to perform stack-relative addressing (got to get SP into 
X, Y, or Z) for stack-local variables, etc.

Compare that with the TI MSP430.  16 16-bit registers, PC is R0, SP 
is R1, Status is R2, R3 is a "constant generator" and the rest are 
uncommitted.  Von Neumann architecture, 7 addressing modes...

The 8051 is a little clumsy, but a genius compared to, say, the 8x300 
uC.  

But C can probably be implemented on any binary uC, given enough 
ugliness and memory. 

Cheers,
Chuck





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