GAL16V8 from 19 years ago

Thread Starter

Ian0

Joined Aug 7, 2020
4,863
This is the printout (the only data I have) from a GAL first used in 2003. (Not exactly a FPGA, but the closest section I could think it might belong in)
In the Programmed Logic section, I think that the exclamation mark signifies inversion, like it does in C.
I’m puzzled by the next section (which the printer spread over two pages).
The exclamation marks appear on all the pins that are outputs. I suspect that the no longer refer to an inversion of the logic, but may signify that they are outputs?

Can anyone confirm.? The second page appears first, I can’t seem to get the iPad to put them in the correct order.
E21678D1-791C-47FB-B558-74D04905D2D3.jpegF307D627-13DB-4B2A-92AC-19E01A28DAD6.jpeg
 

Thread Starter

Ian0

Joined Aug 7, 2020
4,863
Thanks for the useful suggestions.
As you can see from the logic equations, it doesn't exactly do anything complicated: four AND gates, two NAND gates and two inverters, so I was just going to replace it by - you've guessed it - a 74HC08 and a 74HC00 and save 100mA of supply current, but I was puzzled by the "P16V8R Chip Diagram" which has exclamation marks on all the outputs.
Does that exclamation mark mean inversion (as it does in the logic equations) or something else?
 

Ian Rogers

Joined Dec 12, 2012
988
Peronally! I think that was pre-programmed as the script say's its active low.. That must be the datasheet for persons regarding that particular device.... Sinclair used a GAL on his microdrive and gave a similar datasheet..
 

drjohsmith

Joined Dec 13, 2021
383
Thanks for the useful suggestions.
As you can see from the logic equations, it doesn't exactly do anything complicated: four AND gates, two NAND gates and two inverters, so I was just going to replace it by - you've guessed it - a 74HC08 and a 74HC00 and save 100mA of supply current, but I was puzzled by the "P16V8R Chip Diagram" which has exclamation marks on all the outputs.
Does that exclamation mark mean inversion (as it does in the logic equations) or something else?
You have the data sheet link above ,
So you can check inverted or not .

By memory is that the gal is not fixed inverted output unlike some earlier plds .

One reason these things were used , was the just in case.
Try a simple coolrunner cpld .
 

Thread Starter

Ian0

Joined Aug 7, 2020
4,863
I managed to find one, and a plug-in prototyping board.
I can confirm that the exclamation marks in the logic equations signify inversion, but the ones in the chip diagram don’t.
OLLout on pin 18 is high only when both OLL and LDEL are high, so it’s an AND gate, and there is no inversion on the output.

The device has an ex-or gate as part of the output block ( as @drjohnsmith said). I was expecting the exclamation marks in the chip diagram to indicate that the output block was set to invert, but it is not the case.
 
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