lacasse@randvax.UUCP (Mark LaCasse) (08/21/85)
I am looking for a CMOS (or SOS) microprocessor (or microcomputer) for a
personal project that has the following mandatory and desirable
characteristics (listed in order):
Mandatory: 1. Very low power consumption (prefer say 3V, 200uA, at
50KHz clock)
2. 1K on-board RAM
3. Enough on-board EPROM (or PROM or EEPROM) for a
down-load program to fill the RAM with software
serially on one of the uP's pins; or a built in serial
down-load capability (as some non-CMOS uP's I've seen
have)
Desirable: 1. On board clock register or counter/timer
2. Cross C compiler available
Have any leads? THANKS!
Mark LaCasse qantel!hplabs!sdcrdcf!randvax!lacasse
c/o The Rand Corporation cbosgd!ihnp4!sdcrdcf!randvax!lacasse
1700 Main Street lacasse@Rand-Unix
Santa Monica, CA 90406
213/393-0411 ext. 7420john@hp-pcd.UUCP (john) (08/24/85)
<<<< < < < < Mandatory: 1. Very low power consumption (prefer say 3V, 200uA, at 50KHz Your two major choices will be between a single chip microcomputer with built in ram and eprom or building a system with a microprocessor and external memory. The active currents from even CMOS memories can be in the tens of milliamps so it will be difficult to design a system with external busses and still reach 200 ua. Why 50 Khz? Most CMOS micros will operate straight from an AT cut crystal if you can run it greater than 800 Khz (or find an At cut crystal less than 800 Khz). 50 Khz (or 32,768 hz if you want something really useful) will require an external oscillator and its associated power. Running a CMOS processor slower to save power doesn't always work. If you cut your clock rate in half you cut your current in half but it takes twice as long to finish a job. The number of amp*hours required to perform a specific task is independent of clock rate. You can achieve an effective battery powered design by running your processor as FAST as you can while it has something to do and then shutting it down into a low power state when it is finished. I did a design with a MC146805G2 using a 1 MHZ clock crystal this way. The timer would "wake" up the cpu every 128 ms to update the time and do some checks and calculations before going back to sleep. The typical current at 3 1/3 volts was about 160 ua. Running it at 100% duty cycle used less than 6 ma. < < < < 2. 1K on-board RAM < Tricky. Most common CMOS single chip micros have from 64 to 256 bytes and are designed for rom/eprom based applications. You can add external memory but the most common ones have 10 to 30 ma active currents and will blow away your power if you are executing from them. If you need low power data storage then the best way are these "serial" rams that connect via a three wire SPI interface to the micro. I know National makes them and I believe that most vendors with a complete family will offer them. If you must use external memory then try for the "Synchronous" over the more common "Asynchronous" kind. The Async draws active current whenever it is Chip selected and will be a constant load even if you run down to 50 Khz. The Sync rams draw current only at the chip select transitions and are better for low frequency operation. < < < 3. Enough on-board EPROM (or PROM or EEPROM) for a down-load program to < fill the RAM with software serially on one of the uP's pins; or a built < in serial down-load capability (as some non-CMOS uP's I've seen have) < The MC1468705G2 that I used for prototyping has >2K of Eprom. Bear in mind that most vendors make CMOS single chip micros as mask parts for large volume orders. The eprom versions are typically used as developement tools and are priced accordingly. < < Desirable: 1. On board clock register or counter/timer < Most vendors offer this feature < < 2. Cross C compiler available < Don't count on it. Assembly language is the most effective tool for the normal applications that these chips are designed for. Some of them even have enhanced bit manipulation instructions that saves a lot of code. < < Have any leads? THANKS! < Some "leads" in no particular order Motorola 146805 family Intel MCS 31 and 96 families National COPs RCA Hitachi Mitsubishi Nec John Eaton !hplabs!hp-pcd!john