Super turbo PCB layout

بواسطة Pentarou

Hero (513)

25-04-2021, 20:44

Gal scarce, seriously? Do you need a truckload of them?

Edit: Lattice and Atmel (Microchip) still sell them, in DIP packages too.

بواسطة sdsnatcher73

Prophet (3845)

25-04-2021, 20:43

Pentarou wrote:

SkalTura wrote:

An SMD version of the Z80 would be possible too, but that would make the design of the board even more difficult to get all the Z80 pins to line up with the original DIP40 layout of the MSX PCB...

AFAIK the 2 commonly available SMD versions of the Z80 (SOP & QFP) have an 1/1 relationship (same pin#/function) with the DIP pinout, very easy to adapt.

This would be very cool to put on one print with the other components and build a very compact drop-in replacement.

بواسطة jltursan

Prophet (2619)

25-04-2021, 21:34

Pentarou wrote:

Gal scarce, seriously? Do you need a truckload of them?

Edit: Lattice and Atmel (Microchip) still sell them, in DIP packages too.

Good ones. I'm sick of throwing GAL ICs to the dustbin after find them not 100% in working state. At least when they come from chinese sellers, my last good batch came from JAMECO and well, they worked

بواسطة Pentarou

Hero (513)

25-04-2021, 22:20

So? You are buying cheap stuff expecting to get the same quality of reliable sellers, that's your problem.
What has this to do with the fact that GAL are STILL MADE and sold?

بواسطة SkalTura

Champion (399)

26-04-2021, 08:30

Pentarou wrote:

AFAIK the 2 commonly available SMD versions of the Z80 (SOP & QFP) have an 1/1 relationship (same pin#/function) with the DIP pinout, very easy to adapt.

Yes, but that is not what I meant...
The QFP for example is square, so some of the traces will need to go around the chip to the DIP pinout of the Z80 socket on the MSX PCB. That make it a lot more difficult to design.
If you search online for a QFP to DIP adapter board and look at the traces, you will understand better what I mean.
You will have a lot of traces of the QFP on one side, so all other components will have to to go on the other side of the board.
But if you would have the PCB made by a company anyway, then a multilayer board (4 layers for example) will be much easier to design.

بواسطة SkalTura

Champion (399)

26-04-2021, 08:39

If someone could explain exactly whats needs to be on the board, I will give it another try with an SMD version of the Z80 already on the board, and using the schematic with the 74HC components...

Please provide the following information:
- What version of Z80 would you like to use (model/type and package)
- 1 or 2 crystals, and which one (X1 or X2 if that even matters)
- do you need all the inputs (D1 to D6) or is only the IORQ signal connected to pin 20 enough
- do you need an external switch (as drawn in the schematic)
- do you need the Turbo LED on the board, external, or maybe not at all
- would you be comfortable soldering even smaller resistors (for example the 0603 which is 1.5mm)
- double sided board, or is multilayer (4 layers) also an option

As much information as possible please...

بواسطة SkalTura

Champion (399)

26-04-2021, 11:26

Pentarou wrote:

There's a 3rd version, it condenses the TTL ICs in just one GAL/PAL.
Just one chip and it also can (could) provide software enable/disable.

Problem with GAL is that it needs to be programmed, and most people can't do that.
So they will never be my first choice to use, eventhough it will save space on the PCB...

بواسطة SkalTura

Champion (399)

26-04-2021, 11:53

Pentarou wrote:

AFAIK the 2 commonly available SMD versions of the Z80 (SOP & QFP) have an 1/1 relationship (same pin#/function) with the DIP pinout, very easy to adapt.

Only one I can find is the 44 pin QFP version by the way, not a SOP version...

بواسطة sdsnatcher73

Prophet (3845)

26-04-2021, 15:13

QFP is good, I would say use the 8Mhz version. If it is switchable between standard 3.58MHz and double 7.16MHz that is enough imho. WRT production I would think there are enough people in Europe who could build these in batches and also build it into people‘s computers (for everyone not competent/confident enough to do it themselves, myself included).

بواسطة Pentarou

Hero (513)

26-04-2021, 18:55

SkalTura wrote:

Only one I can find is the 44 pin QFP version by the way, not a SOP version...

TMPZ84C00AM is the SOP version, can be easily found on EBAY when searching for "Z80 neogeo".

Quote:

Problem with GAL is that it needs to be programmed, and most people can't do that.

True, but many cheap EPROM programmers can do it, and this project isn't really for inexperienced people.