Hi, im looking to purchase / sample some static ram for a project im going to be working on however i cannot find any suppliers carrying either any ram or any of the right amount. Ive even looked on farnell which i thought had everything. Im looking for a 256K x 1 Bit 5v ram chip in DIP packaging timing isnt the most critical. Ideally something along the lines of the CY7C197N Any ideas where i can get some without paying the earth? Thanks EDIT: Ive checked Rapid, Maplin, Farnell, RS, Digi-Key and Futurlec none seem to have any
256k x 1bit havent seen it before, "x1 bit" do you mean "x1 byte" ??? usually memory is organized as arrays of 8bits or 1byte. am also in a search for SRAMs, futurlec seems too be my choice because it accepts paypal and the international shipping is 5USD since i live in KL(4USD in your case). i will make the purchase + other stuff, when the DAMN ****ing BANK ACTIVATE MY CARD. its been 3 weeks and everybody has a different story and nobody want to help or do their job, damn i got to leave this country. i think i said enough and here is the link btw : http://www.futurlec.com/ICRAM.shtml
Hey, yeah im after 1 BIT not 8 BITS and futurlec dont offer anything like that. I was something with a 18 bit address line and a 1 bit data bus. like the aforementioned CY7C197N see (http://www.datasheetarchive.com/pdf/1132869.pdf) or something with CAS and RAS and less address lines although i think they are only on DRAM as thats all ive seen them on?
How were you planning to handle the rest of the controlling logic ? Microcontroller, logic IC's, CPLD, something else ? Maybe you could use 8- or 16-bit wide RAM and serialize it to the output. With wider bus you would probably be able to get better bandwidth to the RAM still running it at lower speed. As if you're reading from the RAM all the time then you don't have time for write cycles unless you have pauses in the reading or run the RAM faster than you consume the data and figure out some kind multiplexing scheme for reads and writes. Ok, that was just based on my guesses of what you were thinking of doing and maybe you have already figured it out how to get the result you want so in that case just ignore me.
The ram is going to be for that Planar Display i just bought in the forsale thread. I plan to control it with a PIC and use the RAM as the Video Data input and have each pixel addressable in memory. The display is 640x200 which is 128000 pixels now if I use 256K or ram i can have two page files e.g. 2 x 128000 = 256000 which is less than 256k (1024 x 256 = 262144) so i have the first page file in the first 128k and the second in the second. Having the pic refresh the display from one page file and modifying the second and then switching. Or at least that was the plan
So were you planning to connect the RAM DOUT pin straight to the display and then drive the RAM address and read strobe lines and the display control lines with the PIC ? Have you made any calculations how fast speeds you can get with the PIC using this method ? I guess that to get good brightness with the EL panel you need 60-70 Hz update. Also if you are using half of the RAM for refreshing the screen and the second half for writing the new image you need to use the same address lines for reading and writing. So you need to reserve bus cycles also for writing if you want to update the data in the RAM while refreshing the panel. Quickly calculating 640x200 resolution is 128000 pixels per frame. With 70 Hz refresh rate that is 8960000 pixels per second. So for pixel clock with two clock edges per pixel you need to generate 17920000 state changes for the display VCLK pin. Then add the overhead of changing the address lines state also 8960000 times per second and the other control signals. This is just for refreshing the display. Then add writing to the RAM to put the new image data in there. It has been some time since I have used a PIC so I'm not very familiar of the capabilities of the latest ones but you should make some calculations about what kind performance you expect a PIC to provide for you and if it matches the needs here. Maybe adding some logic in addition to the PIC would help.
Hey, what sort of thing would you suggest since most pics wont run above 10MIPS im gonna have to rethink this but i was planning on doing some initial tests to figure this stuff out when i get the display probably tomorrow
You could try to use some logic circuitry to do the refreshing and driving the control signals. Use some programmable logic like CPLD or FPGA or then some logic IC's. Instead of doing the whole functionality with logic circuits you could also try only doing enough of the fast repetitive signal generation to allow the PIC to keep up and let the PIC do the rest of the work. For example if you needed the PIC to interfere only once per line you would already have 640 times less work to do.
