Memory expansion
ZXNet echo conference «hardware.zx»
Hello, All
As I wrote here, I got a hitherto unknown to science clone called
"Duet" Lianozovsky plant. The autopsy showed a fairly standard 48K circuit
with one memory block but without WAIT.
I decided to modernize it slightly - expand the memory. An estimate showed that
you need about 5-6 cases for 128K, not counting the memory itself.
I didn’t want to block the 2nd floor, so I pulled out RU5 and installed RAM
at 256K. And instead of loose powder I installed XILINX CPLD. It is more compact and solderable
much less wires. The picture is attached.
ROM from the branded 128 works quite well.
Now the question. I only use half the memory, and the logic in CPLD is still
There's a lot left to do. I can make as many ports as I want. So this is how most
Is it meaningful to switch memory? Start 1FFD? Which address bits to consider? From
Why is it better to take the firmware so that the maximum
could I use 256K?
File: cpld.jpg http://zx.pk.ru/attachment.php?attachmentid=1940
Hello Specter
Spe> Port #1FFD, bit 4. Supporting software will work
Spe> Scorpion/KAY 256. Pentagon 256 is a rare thing, not all software will understand.
Spe> ATM - rarely supported. Another good option #DFFD (Profi, 0th
Spe> bit), is well supported, there will be fewer problems with programs
Spe> which are accessed via OUT (#FD),A (if you still have hard decryption
Spe> port made), since the probability of meeting LD A,#DF:OUT (#FD),A
Spe> much less than LD A,#1F:OUT (#FD),A.
I was leaning towards the Scorpion 256 option. The only question is how detailed
decipher the address? I heard that there are problems with full decryption.
So far I have A0=A14=1; A1=A15=0 for FFFD.
How many bits does Scorpio have in 1FFD?
And one more thing - what software will support it? ROM 128 tests all memory so I know
that all is well for now. Of course, I can write a test of the top pages myself, but probably
already there. And not alone :)
Hello, ewgeny7
ewg> What software/hardware do you use to flash PLD?
Xilinx ISE 6.3. It's free on their website. And there is also a cable diagram for LPT
for firmware. Parallel cable III.
Hello alexfreed
ale> And instead of loose powder I installed XILINX
What software/hardware do you use to flash PLD?
Hello alexfreed
ale> I was leaning towards the Scorpion 256 option. The only question is how much detail
ale> decrypt the address? I heard that there are problems with full
ale> decryption.
ale> So far I have A0=A14=1; A1=A15=0 for FFFD.
ale> How many bits does Scorpio have on 1FFD?
According to the documentation: port 1FFD -
a0, a2, a5, a12 = log.1,
a1, a14, a15, IORQGE = log.0.
port 7FFD is the same, only a14 = 1.
Hello alexfreed
put the Scorp and SMUC ports there, at least you can work with the screw
Hello, ewgeny7
Port #1FFD, bit 4. Software supporting Scorpion/KAY 256 will work.
Pentagon 256 is a rare thing, not all software will understand it. ATM - rarely supported.
Another good option is #DFFD (Profi, 0th bit), it is well supported, it will
fewer problems with programs that access via OUT (#FD),A (if you still
did a hard decryption of the port), since the probability of meeting LD A,#DF:OUT
(#FD),A is much smaller than LD A,#1F:OUT (#FD),A.
Hello, ewgeny7
ale> Now the question. I only use half the memory and logic in CPLD
ale> more
ale> there is a lot left to turn.
So make a bunch of options for using 256k, attach a couple of buttons and LEDs
;)