ses@mhuxu.ATT.COM (attt-smith, stephen) (06/15/91)
I need a byte or block programmable non-volatile memory source to hold 512 bytes. The total current draw must be less than 75mA. In the non-operating state there can be no power. The application is for programmed memory dialing from a telephone which may not have any internal or external power when it is not being used. The program memory is to consist of 18 numbers of 15 digits. Maybe a microcontroller with EEPROM would work, but I'm only going to make a few of these telephone sets. Any other ideas would be greatly appreciated, please be specific where possible. Stephen Smith ses@mhuxu.att.com 908-851-3728
jon_sree@world.std.com (Jon Sreekanth) (06/19/91)
In article <1991Jun14.173237.22353@cbnewsm.att.com> ses@mhuxu.ATT.COM (attt-smith, stephen) writes:
I need a byte or block programmable non-volatile memory source to hold 512
bytes. The total current draw must be less than 75mA. In the non-operating
state there can be no power. The application is for programmed memory dialing
from a telephone which may not have any internal or external power when it is
not being used. The program memory is to consist of 18 numbers of 15 digits.
Not sure what you mean by "byte or block programmable". If you anticipate
infrequent programming, you can use a serial or byte-wide EEPROM. Serial
EEPROM's are very cheap, 1K bit 93C46 is an 8 pin serial EEPROM, shift in
address, shift out 16 bits of data at a time. (~$1.50) I think you get upto
4K bits in the same package, but don't know the part number. Standard
byte-wide EEPROMs are made in the same pinout as EPROM's, and start
with 28XX; so a 2K byte chip would be 28C16. Being CMOS parts,
they draw well under 75ma.
For frequent updates, there are two choices (apart from taking a
standard RAM and doing your own battery backup). One is the so-called
non-volatile RAM's from Dallas Semi, and others, which have their
own internal lithium battery. They have SRAM speed read and write,
but hold data automatically on powerdown. The other option is the
new flash RAM's, but I've never used them myself.
/ Jon Sreekanth
Assabet Valley Microsystems Fax and PC products
346 Lincoln St #722, Marlboro, MA 01752 508-562-0722
jon_sree@world.std.com