Different kinds of ROM's
To: ab_malek@bbmb.com.my (Abdul Malek Mahmood)
From: Jaap van Ganswijk <ganswijk@xs4all.nl>
Subject: Re: Special progrem need be embedded on chip
At 13:33 1997-07-31 +0700, Abdul Malek Mahmood wrote:
>Dear Mr Ganswijk,
>
>I would like to get some clarification on embedding special program on the chip which
>will fixed on the wrist watch. Following are the question :
>
>1. How can I restore a program to a chip?
This depends on the technology used to store the program.
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:
www.xs4all.nl/~ganswijk/chipdir/ext/mail.htm
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?
I would recommand always to use C, but for small projects
assembler can also be used.
>3. How much do I have to spend per chip?
This depends on the functionality that the chip
offers and also if it has expensive parts like EEPROM
and FLASH and D/A and/or A/D convertor.
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.
I don't understand what you mean.
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.
I don't know. ;-)
Atmel's AVR processors are becoming very popular at the
moment, so perhaps you should check them out first.
