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Erasing time on FLASH microcontrollers

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Jos Brink

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Jan 28, 2004
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I was wondering..

I used to program Atmel AVRs, and now ive started on a C51 chip also from Atmel. I program the avr using ISP (SPI) and the 89C51 using USB. Why does the erase cycle on the 51 chip (with usb) takes longer than on a Avr? The avr even got more program memory. Has this anything to do with the chips stucture? or is it a programmers issue? USB is much faster than SPI programming isn't it?

Does someone regonize this?

let me know ;)

greetings from holland

Maximum speed of USB port is much faster than ISP (parallel port), but USB may use in lower speed than ISP.
Next note;
Erase/programming time depend on IC structure(mostly its memory) and may vary from IC to IC.

The erase time is very different between devices. One big difference is the technology the flashes are made. In general larger Flashes are mostly in newer technologies. Most AVRs are build in newer techologies than most 51s, therefore the erase time is usually shorter.

Whether USB or SPI programming (did you mean SPI or ISP through UART?). is faster depends on the software driver. The maximum data rate is an indication how fast it CAN BE DONE, not how fast it actually is.

Between UART and USB, it would need a strange USB program to be slower than a UART. Between USB and SPI it depends on the clock of the SPI, e.g. some ARM7 devices clock the SPI with 30 mbit/s and it has a lot less overhead than USB.

Cheers, Bob

    Jos Brink

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