Hi guys,

Can someone please tell me what is the right way to wire up memory to S1985 chip?

Ideally with 256K word x 4-bit memory, like 44256 ICs...

Here are the specs of S1985:

http://www.msxpro.com/hardware/datasheet/S1985.zip

Doesn't that depend on the computer it's in? Usually you'd need to grab an extra address line from a tp on the mainboard.

What's tp?

transistor pair? toilet paper? :/

hehe, as far as I'm concernder, all that matters for 64KB block of ram is /CAS /RAS, D0-D7 and AB0-AB7.

To address the whole 512KB of DRAM supported by S1985 (i.e. any MSX-2), I probably need to somehow use AB14, AB15 and/or SLT00/SLT01/SLT02/SLT03 and/or SLT30/SLT31/SLT32/SLT33 signals to select a block of RAM in my DRAM chips...

And since I am a total idiot in signals and inner DRAM working, I was hoping someone with good architecture understanding could give me names of signals and how they should interact with memory banks, through some multiplexers or demultiplexers if necessasy...

Quote:

transistor pair? toilet paper? :/

How could you leave out tiny penis?!?

nah, SLT00/SLT01/SLT02/SLT03 and/or SLT30/SLT31/SLT32/SLT33 signals not got nothing to do with the RAM memory and his mapper.... Its just are the slot and subslot select lines-.

you need the line MA4 (mapper address bit 4) or maybe called on the doc MA18 (memory address bit 18) , but check at the mobo if it are already conected.

i check and is called MA18 but is a shared line......

i read the doc now, and it got a problem, MA18 is a shared line with KBDIR

So, if your computer got a external keyboard, like a PC keyboard, or something like that, you can't use the line MA18 almost you makes a logic device, but, can be already done on the mobo.

Now, if your computer got the keyboard mounted on the case as my msx2, you can use freely that signal, but still need some logic, that can be already done on the mobo....


the logic consist in disconect the CS line of the memory actualy mounted.
using a 3 state chip ( i are lazy for get the ECG book right now), and to use the MA18 for redirect the CS line to the original memory chips or other mounted ON that chips.. with a independient CS line. ofcourse using the same chips part.

don't forgot to support the refresh signal

Yeah, well, I remember seeing schematics of russian MSX-2 computer somewhere. If it's not too bad, I might pick up the signals for internal dram from it...

If anyone can provide clean english schematics of any MSX-2 computer, please let me know! I will be very grateful!