Request for PALASM Guru

[Kchula-Rrit]

I've managed to program a GAL for my RAM-ROM cartridge.  It seems to pass my rudimentary testing, using an 8-pin DIP switch and some LEDs.  However, I'd like for someone who knows more about PALASM than I do to look it over and and see if it seems reasonable.

 

My intention is for the bottom 7K of the cartridge space to be EPROM, and the top 1K be RAM.  The EPROM is a 512K, split into 64 7K banks.  I know it's technically 8K per bank, with 1K wasted.  The RAM is 64K, likewise split into 64 1K banks.

 

The RAM and ROM banks can be independently selected by writing anything to 60XX for EPROM, and 70XX for RAM.  The least-significant eight bits are written into the bank register.  The bank-number is left-shifted by one bit, so writing 6002/7002 selects Bank 1, 6004/7004 selects Bank 2, up to 607E/707E selects Bank 63.

 

I've attached the PALASM source file, along with the equivalent schematic for the GAL and the entire cartridge.

 

K-R.

 

CART-PLD.PDS RAM-ROM Cartridge.pdf

RAM-ROM Cartridge PLD Schematic.pdf

Edited April 8 by Kchula-Rrit
Used old schematic for PLD

[matthew180]

What manufacturer and specific part number did you end up with, and what programming tools are you using?

 

When I was doing PAL/GAL programming, I used Lattice ispLeveler Classic, which allows writing the logic using HDL (VHDL in my case).  I never learned PALASM, and although it looks somewhat straight forward, using an HDL would be easier, faster, less error prone, IMO.

 

[Kchula-Rrit]

12 hours ago, matthew180 said:

What manufacturer and specific part number did you end up with, and what programming tools are you using?

The part is a Lattice GAL16V8D-25LP.  I bought three of them, but for future projects I'd probably use the ATF part.  I used PALASM to "compile" the CART-PLD.PDS text file, and programmed it with a MiniPro T48 programmer.  Tested with an 8-pin DIP switch on the inputs and some resistor LEDs on the outputs.  The data sheet says the inputs have internal pull-ups.

12 hours ago, matthew180 said:

When I was doing PAL/GAL programming, I used Lattice ispLeveler Classic, which allows writing the logic using HDL (VHDL in my case).  I never learned PALASM, and although it looks somewhat straight forward, using an HDL would be easier, faster, less error prone, IMO.

 

I found out about PALASM in the Inexpensive way to try out GALs? conversation.  It's free, so I thought I would give it a try.  I should take a look at HDL, I guess.  It would be really cool if there were a program to convert a schematic into a GAL/PAL programmer file.  I have a "Make: Programming FPGAs" that talked about such a thing; don't know if there's one for GALs/PALs.

K-R.

[matthew180]

https://github.com/hneemann/Digital

 

"Direct export of JEDEC files which you can flash to a GAL16v8 or a GAL22v10."

 

GALs are getting harder to find support for, and the best options seem to be some form of PALASM, CUPL, or ABEL, and some various of the open source tools.

 

I was recently introduced to Renesas "GreenPak" devices, which come in small packages and can cost as little as $0.50 (a 20-pin device that would easily replace a GAL is about $1.32).  It has current software support for Linux, MAC, Windows, and the screenshots look very schematic and drag-n-drop.  The specs of the devices are nice and it appears they can go to 5V Vcc, and therefore can support 5V TTL directly.  I have not used any yet, but they look nice.

 

https://www.renesas.com/us/en/products/programmable-mixed-signal-asic-ip-products/greenpak-programmable-mixed-signal-products

 

As for validating your PALASM, I hope someone who knows the language and has some spare cycles will chime in.  It looks easy enough, and if your chip works as expected then that is probably the best validation you can get.

 

[Kchula-Rrit]

Thanks for the suggestions.  I tried playing with DIgital a little, and it's fascinating.  Looking at it, I realize I have to update my equivalent schematic to match my PALASM equations.  Then I can see if Digital can come up with the same JEDEC file.

Took a look at the GreenPak page-- wow!  I wonder if the electric corkscrew and suntan monitor are not entirely serious.  From the suntan monitor PDF file:  The task is to inform a sunbather when to turn over (or go home) after receiving the desired accumulated dose of sunlight...

K-R.