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Different kinds of ROM's

From:    Jaap van Ganswijk <ganswijk@xs4all.nl>
To:      Abdul Malek Mahmood
Subject: Re: Special program need be embedded on chip

On 1997-07-31 Abdul Malek Mahmood wrote:

I would like to get some clarification on embedding special program on the chip which will fixed on the wrist watch. Following are the questions:

1. How can I restore a program to a chip?

There is:

• ROM
• (OT)PROM*
• EPROM*
• EEPROM*
• Flash

• A device with ROM is mask programmed which must be done by the manufacturer.
• An (OT)PROM* can only be programmed once using a normal EPROM* programmer. Fuses are blown, that's why it can't be erased anymore. Some (OT)PROMs are just EPROM*'s without a window for erasing the ROM again. In this case there are no fuses blown, but erasure is made impossible.
• An EPROM* is programmed using an EPROM* programmer, which is a device that can apply programming voltages like 12.5, 21, 25 V. The devices can be erased again by UV light.
• EEPROM* can generally be programmed by the chip itself using a bootloader which is in a ROM part of the processor (I think).
• Flash works about the same I think, but can only be erased per page (?).

The last two can be erased electronically by the program itself (which must be in ROM or another part of the EEPROM* or Flash, but I don't have much experience with these.
Perhaps you' better ask on the PIC and/or Atmel mailing list, see: local

The program is generally downloaded via the serial port I guess.
An EPROM* programmer is generally also connected via a serial port or the printer port or it's inside a PC.

2. Normally what language (High or Lower level language) should I use to program?

3. How much do I have to spend per chip?

Microcontrollers go from $0.50 or so to $100 a piece.
Generally: The more pins they have, the more expensive they are.

4. Can I have the registered manufacturer - reputable one preferbly the Malaysian manufacturer.

First you'll have to find a processor that fits your needs and then you should find your local distributor. Or in fact while deciding which processor to use you probably already talk to several distributors to ask for data sheets and ask how easy certain processors can be delivered and what they cost. You can also ask them which processors most of your colleagues are using...

5. How can you best assist me in this area.

Atmel's AVR processors are becoming very popular at the moment, so perhaps you should check them out first.