The "BEST" 8 bits micro

[eltonjohn]

ds89c420 instructions

Well i had a very specific need in a recent project i needed to sample a digital signal at 8 Mbits/s .. To do that with no specialized logic i needed a CPU with a very efficient instruction set . Also the price was an issue!.

After carfull examination of the Cygnal51 , the AVR the MSP430FXX , The pic and even the PSOC from Cypress .

I concluded . that Cygnal51 and the AVR are very similar in the power of their instruction set . Cygal51 has only the advantage of the speed they have now a version running at 50Mhz and 100mhz .. Fastest Avr the Mega familly is only 16Mhz .. Otherwise the price is a tradeoff between flash an SRAM campability .
But for the same Speed i think that Cygnal51 is better priced !.
But this can be just only the beginning of a long consideration with adepts in both sides .. But for me both chips deserve de first PLACE ...
The second Runner up goes to the TI MSP430 familly . and the PIC ..
It is hard to give second and third place . Because both chips are so different and the CRITERIA for me was the INSTRUCTION set ..
The Ti chip is a 16 bit chip . So to acomplish the same it requires more code espace . But its frequency is 8 Mhz and most of the instructions require 2 to 3 cycles .. The Pic in the other hand runs at 20Mhz but the instructions take 4 or 8 clocks to execute . So PIC and TMS430 are also very similar in this respect .

I didn't take in account the number of on chip peripherals . My Need was very precise .. TO SAMPLE a pin PORT and to store the value , to make a comparaison with a variable and if a match to jump.
Both chips AVR and cygnal do the JOB .. .. Imposible to do with all others !

 

[ME]

Actually the PIC18 runs at 40 MHz and not 20 MHz!
But PIC18 have 4 Clock-Per-Machine Cycle (Oscillator clock cycle is divided by 4 internally).
So it can perform up to 10 MIPS.


Dallas Semiconductor (Maxim) also makes some very fast 8051-compatible microcontrollers.
www.maxim-ic.com/MaximProducts/Microcontrollers/HighSpeed.htm

The fastest it the DS89C420: Ultra High-Speed Flash Microcontroller (33 MHz, 1 Clock-Per-Machine Cycle, up to 33 MIPS):
**broken link removed**

INSTRUCTION SET
The DS89C420 instructions are 100% binary compatible with the industry standard 8051, and are only different in
the number of machine cycles used for the instructions. Some special conditions and features should be
considered when analyzing the DS89C420 instruction set. Full details are given in the Ultra-High-Speed Flash
Microcontroller User’s Guide.

 

[eltonjohn]

Ok i have now to TODO some CALLINGS here !

A lot of chip MANUFACTURERS give THE MIPS mesure OF THEIR PRODUCTS .. This is is a very MISLEADING indication of the PROCESSING POWER of A CHIP .. Cygnal is announcing its 100 Mhz chip .But is only 100 MIPS PEAK ! ..with only 20% of their instruction capable of reaching that peak .. In more standard terms the tipical most commun instruction will be executed in 2 to 3 instruction . wich places the RAW power of that chip in around 40 to 50 MIPS .. the AVR is another chip chip with also the same a typical 16 Mhz chips will have a 8 MIPS RAW power MEASURE !
The PIC even at 40 MHZ will be around 5 MIPS .. The more POWER you have the more YOU have to go to FETCH DATA or Write DATA OUTSIDE de CPU'S REGISTER FILE . The more HEAVY PENALTY INSTRUCTIONS will be EXECUTED .. Typically LOAD and STORE INSTRUCTIONS demand 2 to 3 execution CYCLES (NOT CLOCK CYCLES sometimes LIKE IN THE PIC CASE )

 

[ME]

Yes I'm well aware of this fact.
That's why I wrote up to 10 MIPS for PIC.
I know this is very teoretically.
I could have written minimum execution time for PIC18 is 100 ns.
Maybe this is less misleading.

Another very fast 8-bit MCU is the UBICOM SX (fomerly SCENIX) which is a very fast PIC 16C5X clone.

Minimum execution time for different 8 bit MCU's:
Cygnal (8051) @ 100 MHz: 10 ns
UBICOM SX (PIC16C5X clone) @ 75 MHz: 13.3 ns
Dallas DS89C420 (8051) @ 33 MHz: 30.3 ns
Atmel AVR @ 16 MHz: 62.5 ns
Microchip PIC18 @ 40 MHz: 100 ns


You can't compare the speed between of different architectures based on the minimum execution time, but you can compare different MCUs of the same architecture. For example 8051 MCUs like Cygnal and Dallas can be compared directly based on minimum execution time.
From architecture to architecture there is a big difference in the average of instruction clock cycles per instruction.
For the AVR for example most of the instructions are excuted in one clock cycle, while many PIC and 8051 instructions need more than one instruction clock cycle to execute.

I think AVR is the fastest 8-bit architecture if they all run with at same execution time.

I have seen AVRs overclocked at 24 MHz, but I would not reccomend this for commercial products:
**broken link removed**
http://www.ksw-funcard.civ.pl/atmega128/Atmega128.htm
I don't know if it is possible to overclock any of the other MCUs??


If you want an even faster MCU than any of theese you can use an FPGA with a soft MCU core. You can get HVDL and Verilog cores of both 8051, AVR and PIC plus many others.

For large quantities you can also get AVR asics from Atmel running at up to 70 MHz.