My recollection of XRAM is that it's just self-refreshing/multiplexing DRAM, designed to be used as a cheap, pin-compatible replacement for SRAM, but needing a separate clock for refresh, and a longer reset. When I was doing all the investigation/work on DolphinDOS, I recall seeing a memory expansion board for the 1541 that had an Xram option on it. It just needed one additional wire, from memory. I think it was a variant of the RAMBOarD - http://www.lb.shuttle.de/puffin/8k1541/8k1541.html - I MIGHT still have the schematics somewhere - I'll look later. Julian Tuesday, March 11, 2014, 7:30:51 AM, you wrote: > When trying to deal with some 4168 XRAM chips, I couldn’t get them > to work properly. After studying the datasheet I found in the notes: > http://dl.dropboxusercontent.com/u/58002657/4168_notes.jpg > Point [2.] seems important to me but I seem to have problems > interpreting it unambiguously.. or for some other reasons these RAMs still don’t want to work.. > “An initial pause of 2ms is required after power up, followed by > any 8 _CE cycles and 64 _RFSH cycles before proper device operation > is achieved. Read, write, and external refresh cycles may be used as > _CE dummy cycles for initialisation. The 64 refresh dummy cycles can > be performed before or after the 8 _CE dummy cycles. Both dummy > cycles must be within AC parameters. See figure 1, below." > Figure follows as on the picture linked above. How do you > understand the above? How should it be interpreted? Please note that e. g. here: > http://www.smspower.org/uploads/Development/SegaMasterSystemIIServiceManual-1715922A-1.png > the _RFSH is tied up to VCC.. > -- > SD! > Message was sent through the cbm-hackers mailing list -- Best regards, Julian mailto:jp@digitaltapestries.com Message was sent through the cbm-hackers mailing listReceived on 2014-03-11 02:00:07
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