Post by thread:[PIC]: Cheap easy small ram

I'm working on an idea for a robot navigation system using a PIC, but I need approx 2000 bytes or RAM. The ram only needs to be written/read sequentially, but I need decent speed and don't have that many PIC pins. I can spare 8 pins for the data port (read/write) and a clock and reset pin, and read/write pin, is 11 pins total. Maybe 12 pins available if necessary. I don't want to use flash eeprom or any I2C addressed memory as it is constantly reading/writing at a fair speed. ie must be parallel data read/write. Any suggestions for a cheap, minimum chip solution to get the extra 2000 or 4000 bytes of RAM attached to my PIC? :o) -Roman -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

At 10:44 PM 7/5/02 +1000, you wrote: >I'm working on an idea for a robot navigation >system using a PIC, but I need approx 2000 bytes >or RAM. The ram only needs to be written/read >sequentially, but I need decent speed and don't >have that many PIC pins. > >I can spare 8 pins for the data port (read/write) >and a clock and reset pin, and read/write pin, is >11 pins total. Maybe 12 pins available if necessary. > >I don't want to use flash eeprom or any I2C addressed >memory as it is constantly reading/writing at a fair >speed. ie must be parallel data read/write. How about using an SPI addressed FRAM? You'll get really fast access and the newer ones have quite long read/write life (but work it out). SPI access with sequential read is *very* fast, limited mostly by the maximum clock on the SPI port. Some can work at 20MHz. Here is one: www.ramtron.com/products/datasheets/FM25C160datasheet.pdf (5 MHz 2K bytes, 10^10 read/writes life) This 8K x 8 one has unlimited read/writes and operates at 20MHz, but only at 3V power: http://www.ramtron.com/products/datasheets/FM25CL64ds_r0.3.pdf Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam@spam@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com 9/11 United we Stand -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

On 5 Jul 2002, at 22:44, Roman Black wrote: > I'm working on an idea for a robot navigation > system using a PIC, but I need approx 2000 bytes > or RAM. The ram only needs to be written/read > sequentially, but I need decent speed and don't > have that many PIC pins. > > I can spare 8 pins for the data port (read/write) > and a clock and reset pin, and read/write pin, is > 11 pins total. Maybe 12 pins available if necessary. > > I don't want to use flash eeprom or any I2C addressed > memory as it is constantly reading/writing at a fair > speed. ie must be parallel data read/write. > > Any suggestions for a cheap, minimum chip solution > to get the extra 2000 or 4000 bytes of RAM attached > to my PIC? I normally use a 4040 (or 74xxx equiv) counter to supply the address lines. This just needs reset and clock. R/W pin from uP direct to RAM. regards, George Smith -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

At what rate do you access the memory? I have a system using serial eeproms where I buffer the data, interleave between devices, use the devices page mode, and checks to see if the previous write is done. The system is not fully tested yet, but is designed to allow data to be stored at several or even 10s of K bytes per second. Very few parts/pins are needed. I'm sampling pressure and thrust data for a few seconds at 1000 samples per second. I will provide more info if you are interested. Greg {Original Message removed}

Thanks Spehro, (and George too) for the suggestions. I really didn't want to use serial memory as the processor is very busy doing stuff and I can only spare a few instructions to read or write a whole byte. I think I have found a solution with a nifty circular buffer using the PICs internal ram, so I may not need the external memory after all. I think almost any product can be made with one PIC and one transistor... ;o) -Roman Spehro Pefhany wrote: {Quote hidden}> > At 10:44 PM 7/5/02 +1000, you wrote: > >I'm working on an idea for a robot navigation > >system using a PIC, but I need approx 2000 bytes > >or RAM. The ram only needs to be written/read > >sequentially, > How about using an SPI addressed FRAM? You'll get > really fast access and the newer ones have quite long > read/write life (but work it out). SPI access with > sequential read is *very* fast, limited mostly > by the maximum clock on the SPI port. Some can work > at 20MHz. > > Here is one: > www.ramtron.com/products/datasheets/FM25C160datasheet.pdf > (5 MHz 2K bytes, 10^10 read/writes life) > > This 8K x 8 one has unlimited read/writes and operates at 20MHz, > but only at 3V power: > http://www.ramtron.com/products/datasheets/FM25CL64ds_r0.3.pdf -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Greg Oxelis wrote: > > At what rate do you access the memory? > I have a system using serial eeproms where I buffer the data, interleave > between devices, use the devices page mode, and checks to see if the > previous write is done. The system is not fully tested yet, but is designed > to allow data to be stored at several or even 10s of K bytes per second. > Very few parts/pins are needed. > > I'm sampling pressure and thrust data for a few seconds at 1000 samples per > second. I will provide more info if you are interested. Hi Greg, thanks for the help but serial eeproms really aren't fast enough for this app, mainly because I need the processor for other stuff at the time. But I am interested in your water rocket (guessing!!?) ;o) -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Roman, The SPI FRAM can be accessed using just a couple instructions per byte using the hardware SPI. One trick you can use is not to bother checking for the 'completed' flag. You will "know" it has been set after the appropriate number of instructions. By setting the SPI clock to Tinst, you can 'pipelne' access to the FRAM at 9 (maybe 8) instructions per byte. While one byte is transfering you are getting the next byte ready to send (on writes) or processing the previously read byte (on reads). Bob Ammerman RAm Systems {Original Message removed}

Thanks Bob, actually I didn't think of using the hardware SPI. :o) -Roman Bob Ammerman wrote: {Quote hidden}> > Roman, > > The SPI FRAM can be accessed using just a couple instructions per byte using > the hardware SPI. One trick you can use is not to bother checking for the > 'completed' flag. You will "know" it has been set after the appropriate > number of instructions. > > By setting the SPI clock to Tinst, you can 'pipelne' access to the FRAM at 9 > (maybe 8) instructions per byte. While one byte is transfering you are > getting the next byte ready to send (on writes) or processing the previously > read byte (on reads). > ----- Original Message ----- > > > At 10:44 PM 7/5/02 +1000, you wrote: > > > >I'm working on an idea for a robot navigation > > > >system using a PIC, but I need approx 2000 bytes > > > >or RAM. The ram only needs to be written/read > > > >sequentially, -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Fri, 5 Jul 2002, Spehro Pefhany wrote: >Here is one: >www.ramtron.com/products/datasheets/FM25C160datasheet.pdf >(5 MHz 2K bytes, 10^10 read/writes life) > >This 8K x 8 one has unlimited read/writes and operates at 20MHz, >but only at 3V power: >http://www.ramtron.com/products/datasheets/FM25CL64ds_r0.3.pdf Are these on sale somewhere in smally qty? Like Digi-key, Mouser, etc ? thanks, Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body