DIY RAM EXPANSION

[tcat]

Hi All,

I take your advise SRAM and GAL makes a good ground for the design.
I wish to start with an updated GAL equations based on Brane's guidance,
It is commented I hope you can follow.

Code: Select all

GAL16V8
Glue logic for 512x8 SRAM
Sinclair QL RAM Expansion
(c)2014 Sinclair QL forum

# control bits set by assembler
# SYN = 1
# AC0 = 1
# AC1(n) = 1,1,1,1,1,1,1,1

#1   2    3      4      5    6      7     8   9   10
 1   NC   A19    A18    NC   /DS    NC    NC  NC  GND
 0   NC   /RAMCE VALID  NC   /DTACK DSMCL NC  NC  VCC
#11  12   13     14     15   16     17    18  19  20

  # input 1 is wired to VCC
  # input 0 is wired to GND
  # NC - signal not connected
  # / - signal active on low level
  # / NOT, + OR, * AND operators

  # enables SRAM on VALID memory range and data strobe DS
  VALID = A19 * /A18 + /A19 * A18
  RAMCE = VALID * DS

  # start of our cycle DSMCL goes high, else tristate high impedance
  IF( VALID )
  DSMCL = 1

  # end of our cycle DTACK goes high, else tristate high impedance
  IF( VALID * DS )
  DTACK = 1

# END

[tcat]

Brane,

I see your point, finding a suitable place inside QL, on top of CPU where most of the signals are provided already, use IDE ribon cable to make connections. Short and quick uncomplicated path, saving PCB and voltage regulator design.

I am afraid of doing internal upgrades for my lack of skills, for the risk if something went wrong, and also for some QL users might think that internal changes somehow spoil the collectors value.

I was also considering PCB prototype board as one seen on the picture, to test design while not certain but QL forum seems helpfull in this respect.

TCAT

prototype PCB board

[swensont]

> But in that form it is goddamn unuseable. That thing can't even keep the time!

You forget that most computers in 1984 did not have battery backup clocks. The standard IBM PC had to have an add-on board for that. Same with the Atari ST, and pretty much all of the 8-bit systems. Only years later was battery-backed clock a normal feature.

[Peter]

Yes, you could have two expansion back to back theoretically, but that won't be cheap and with foreign object protruding out of left side, result won't feel like genuine QL.

In the eighties, sophisticated QLs had about half a meter of extensions on the left side. So maybe it was "genuine QL"

But I hated it so much that even three decades later, I designed the QL-SD to be purely internal, and not to conflict with other internal extensions like Qimi.

[tcat]

Hi,

Trying to asses the ideal PCB width.
I have only a connector with straight pins, 90 degree angle pins would be better.
I taped it onto the cardboard edge, it inserts inside QL more or less smoothly.

TCAT

PCB width

[prime]

The DIN41462 connectors and the QL expansion cards are designed around Eurocard boards that are 100mm wide, and whatever length is needed.

Cheers.

Phill.

[Dave]

Half eurocard. The nominal size is 100x160mm, but some QL bases vary and have a guide that creates a limit of 98.5mm if you want the connector to line up straight and true. For this reason, I design boards with a nominal 97mm height.

I always, when discussing a board, think of as having directions and a specific orientation. Up, top, and back all refer to the back edge of the board. Down, bottom or front refer to the edge nearest the user. Right is the female connector facing the QL, and left is the thru-connector to other hardware, or sockets and expansions. This was taught to me by Arnie Gardner at Sandy. Apparently, some people considered the QL connector edge as "bottom" and this caused a couple of expensive or timewasting miscommunications between different QL accessory companies when we communicated with each other. Thus a standard was agreed.

With PC boards, the edge facing the back of the case is always the up, top or back of the board.

What I want to know is.... Who is Dawn?

[tofro]

The DIN41462 connectors and the QL expansion cards are designed around Eurocard boards that are 100mm wide, and whatever length is needed.

Right. 50 cm, at least...

But if you're not fitting an angled connector (Dave can tell you where to get them cheap ) your card moves up in the slot into more narrow space.
Do yourself a favor and get the proper connector - It will get quite a bit fiddly to insert the card if its not at the correct height.

Tobias

[tofro]

What I want to know is.... Who is Dawn?

She's living under my Gold card.

[Nasta]

What I want to know is.... Who is Dawn?

She's living under my Gold card.

IIRC girlfriend of the guy who worked with Stuart Honeyball and designed both the GC and SGC PCBs, whose name escapes me...