Post by thread:[PICLIST] [EE] SIMM datasheet

Hi! Please, could anyone post a link where I can found information on how to access a SIMM ram module. I do not want a PIC program for doing that, what I want is just a timing diagram and explanation of the differents signals. For instance, a datasheet would do the job. Thank you in advance. Cheers, Diego. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>Please, could anyone post a link where I can found information on how to >access a SIMM ram module. I do not want a PIC program for doing that, >what I want is just a timing diagram and explanation of the differents >signals. For instance, a datasheet would do the job. Try here http://www.okisemi.com/communicator/public/nf/docs/PrdMemory.html -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Afaik there are no SIMM datasheets, only datasheets for the chips on them. Take a number off of one of them and type it into a search engine or go to the manufacturer and search for it. Hitachi and Motorola come to my mind as well known DRAM makers. The signals are mostly the same as for any DRAM unless you pick EDO or synchronous RAM in which case you are sol imho. A DRAM has three basic control signals: /RAS /CAS and /WE. A SIMM has a /CAS line for each byte in the SIMM width (e.g. 32 bit SIMMs have four, called /CAS0 to /CAS3). There are some more signals on the SIMM that let you talk to the EEPROM on it (if present). Address lines are multiplexed, data lines are not. The timing depends on the exact chips (the BIOS selects appropriate values but you can't - you need to know them first). Older SIMMs use basic DRAM timing (address_low > /RAS > address_high > /CAS for read or /WE for write, and address_low > /RAS for refresh only). Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.