a2retro wrote:
To: Michael J. Mahon Michael J. Mahon wrote:a2retro wrote:To: a2retro a2retro wrote:alex.freed.007 wrote:The 128K version is particularly easy to use with a battery back-up asit has an active high second chip select. Most likely just adding a> diode and a coin cell will make it NV.I have seen this implemented on a few other projects. zxmmc+ for example.I plan to use this approach for my //cmxp project.Cypress also has an interesting part CY14B104L-ZS45XC - combo SRAM/Flash with autosave.GlennFor anyone updating their card to a 512K ram - double check the datasheet from your vendor of choice, as I see there doesn't seem to be a standard on pin A17 and A18. They are interchanged across vendors.Who cares what they label the address pins on a static RAM? It's just address bits in --> data out. -michael NadaNet and AppleCrate II: parallel computing for Apple II computers! Home page: http://home.comcast.net/~mjmahon "The wastebasket is our most important design tool--and it's seriously underused."Okay I see what your saying - it will still work - it just won't be accessed contiguously.
Since we don't know what the manufacturer did inside the chip, "contiguous" is not a meaningful term. The manufacturer's assignment of address bit numbers can be purely arbitrary relative to the logical and physical structure of the chip. The only requirement is that when N unique address bits are presented, a unique and repeatable bunch of bit cells is accessed. Of course, the same is true of the numbering of data bits. -michael NadaNet and AppleCrate II: parallel computing for Apple II computers! Home page: http://home.comcast.net/~mjmahon "The wastebasket is our most important design tool--and it's seriously underused."