The Sinclair QL Forum

RAMCS =
DS * A19 * /A18
+ DS * /A19 * A18
+ FC0 * /FC1
+ /FC0 * FC1

Correct?

Brane, Perfect... I am almost there... I need to fit +5V voltage regulator since expansion connector provides +9V. Also GALs come at different speeds, fasters draw more current. SRAM takes 30mA GALs depending on model from 55mA to 115mA Total max of 145mA I hope it won't need extra heat sink and it ...

Brane, Thank you so far. What do you think of theese equations, I have used from GERT example? I have GAL compiler by V.Bosch (a German lad from Stugardt) for Linux. Tristate equates are handled by IF statements, so I recoded GERT example as follows, GAL20V8 Glue logic for 512x8 SRAM Sinclair QL RAM...

Brane,

I believe somewhere in between or after the cycle SRAM chip should also be dissabled by CS pin, to get high impedance on its data pins, correct?

TCAT

Hi Brane, Studied the document on timing also read through your reply, THANK YOU. What the GAL logic does or should do, in my understanding is this, - when it sees it's own address pull DSMCL high - set SRAM pins CS,OE,WE accordingly - wait for SRAM to complete the fetch/store cycle, that is at leas...

Hi Dave, And thank you for joining in the discussion. I am no good at h/w, I can see your point, GAL is complex, yet can be programmed so is flexible. I read in The QL technical guide that add-on card data bus should be a 74LS245 or equivalent, in terms of drive ability, and being tri-state. Also th...

Hi Brane, Thank you, I am almost getting there. What troubles me is my lack of understanding of GAL that drives the the addressing logic. /DTACK and DSMCL are tristate signals and controlled by /OE pin. Address validity is by VALID pin. At the moment I have /OE put to ground, not sure if that is rig...

Hi All, I am trying to follow in the discusion of the internal ram upgrade. Just thinking if it were possible to make it external memory upgrade throuh the QL expansion port. Please see the schema in which I tried to catch the idea of GERTK's design, though I am not sure I understand all details. ql...

I don't recommend using old type DRAM (dynamic RAM) chips for any new build. Old DRAM chips need some extra circuitry to generate the DRAM refresh signals. Given that static RAM (SRAM) chips of the sizes that are useful to us are now cheap, and are much easier to use, and need less "glue"...

Dear All, I have a plain 128k no TK2 good quality QL, I wish to expand it with a little amount of RAM, to get at least to a double i.e. 2x128k, as was the Sinclair option for QL developers back in 1984. I am not much good at h/w designing as most of you here likely are. I looked at these components ...