simple sram question - Page 1
Forum section: electronics / beginners

author: digitalundernet
author_rank: Contributor
timestamp: March 25, 2012, 07:35:49 pm
content: I can't find this answer on google or the data sheets. When sram says 2mb x 8 does this mean I need 8 chips to get 2mb or is the memory divided up into 8 byte blocks? I think Its the former but I don't know for sure

author: wkb
author_rank: Super Contributor
timestamp: March 25, 2012, 07:37:00 pm
content: Typically means 8 bit wide memory

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 26, 2012, 01:37:00 pm
content: Second wkb.Furthermore, memory is typically specified as something like 2M x 8, not 2Mb x 8.2M translates to 21-bit address space.8 translates to each address being 8 bits wide.Therefore, the SRAM has 16Mbit = 2MByte storage capability.Another example for the sake of completeness: another 2MB specified chip can be partitioned as 1M x 16, which has a 20-bit address space.

author: westfw
author_rank: Super Contributor
timestamp: March 26, 2012, 04:07:59 pm
content: I frequently see some memories described in terms of total capacity, and bus-width. Usually ExPROMs, but still...At 27C512 is a 512Kbit EPROM in x8 organization, for example. A 24C04 is a 4kbit EEPROM. And a 62256 is a 256Kbit Static Ram in x8 configuration. It all depends on where the comma is. "2k x 8" really ought to mean a 16kbit memory, but "2k, x8" is unfortunately common as well, and sometimes the comma is forgotten.Read your datasheets.

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 26, 2012, 06:07:08 pm
content: Quote from: westfw on March 26, 2012, 04:07:59 pmDo you have a specific datasheet you can point to? Did a quick search on the devices you've listed and all appear to specify the standard <address space> x <data width> org convention. It sounds like you're talking about raw array blocks which require peripheral address decode; haven't seen those outside of a textbook description on programmable logic...then again, I'm not nearly as "seasoned" as some people around here.The OP did disclaim his loss for an acceptable answer...I can see where he might be coming from considering how interpretation of the convention assumes an understanding of how memory devices are generally organized.

author: westfw
author_rank: Super Contributor
timestamp: March 27, 2012, 12:22:12 am
content: The part numbers themselves aren't enough?I certainly hope the datasheets are clear enough; it's the marketing dialog and product summaries that tend to get ambiguous. "24c04 4kb EEPROM chip" without a clear indication of whether that's kbits or kbytes. Although, looking around, it does seem to be less common than I remember...

author: slateraptor
author_rank: Frequent Contributor
timestamp: March 27, 2012, 01:14:34 am
content: As previously mentioned, I performed a findchips search on all the part number you listed and looked at datasheets from multiple vendors, none of which showed the atypical specification scheme that you alluded to. Now it just sounds like you're referring to datasheet page-1 marketing rubbish and ambiguity in vendor-specific part numbers...in which case, disregard.

author: westfw
author_rank: Super Contributor
timestamp: March 30, 2012, 12:52:39 am
content: Ah. I see. When I said "read your datasheets", I meant that that was where correct and clear information would be, compared to the ambiguous "4kb eeprom" part description or part number, not that reading datasheets would find you examples of "problem" I was describing.