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# GALs and old PCBs

M

#### matt

Jan 1, 1970
0
I've having some difficulties using a GAL on a 25 year old PCB - I
have the correct JEDEC file and my programmer will handle the GAL okay
(a GAL16V8D-25QPN) but the board won't work with the newly programmed
GAL.

Why is this likely to be?

Something to do with the type of GAL or perhaps even the speed?
(although I would have though that a -25 would be fine for a 25 year
old PCB).

Thanks

D

#### Deefoo

Jan 1, 1970
0
matt said:
I've having some difficulties using a GAL on a 25 year old PCB - I
have the correct JEDEC file and my programmer will handle the GAL okay
(a GAL16V8D-25QPN) but the board won't work with the newly programmed
GAL.

Why is this likely to be?

Something to do with the type of GAL or perhaps even the speed?
(although I would have though that a -25 would be fine for a 25 year
old PCB).

Thanks

-25 is for speed, not for age ;o)

There is no reason to assume that your GAL would be of the right speed for a
25 year old PCB. Your GAL may be too fast or too slow. Don't you have the
original GAL?

--DF

M

#### matt

Jan 1, 1970
0
-25 is for speed, not for age ;o)

I know that.
There is no reason to assume that your GAL would be of the right speed for a
25 year old PCB. Your GAL may be too fast or too slow. Don't you have the
original GAL?

No - the original chip was an 82S153 PLD, it's just that someone
converted the contents of that to JEDEC format to work with a modern
GAL (82S153's are hard to find and expensive). It worked for him, just
can't figure out why it won't work for me.

So perhaps I should buy and try a faster GAL? -15 perhaps? -10? -7?

S

#### Sambo

Jan 1, 1970
0
matt said:
I know that.

No - the original chip was an 82S153 PLD, it's just that someone
converted the contents of that to JEDEC format to work with a modern
GAL (82S153's are hard to find and expensive). It worked for him, just
can't figure out why it won't work for me.

So perhaps I should buy and try a faster GAL? -15 perhaps? -10? -7?

Ah, pals and gals maybe I'll still get a chance to play with those.
I would say you are most likely already way too fast, 250-300ns RAMs in those days, 82S153 probably had propagation delay of at least 40ns come to think of it it is not even PLD it is a PROM hence even larger propagation delay can be expected. A quick glance on goole, I don't see anythink with specs ( so many useless hits these days $#*%^& ) It is not in the "CMOS cook Book" must be in "TTL Cook Book" anybody have it handy? Of the top of my head I don't even think it has an enable signal which you could ..... The old slow part may be bridging the time the inputs stop being valid and the outputs are read (since I don't believe the part has output enable), the only way would be to buffer the outputs or use a device that could delay the outputs internaly. Why it worked for the other person (with same circuit, same speed and type GAL ) can't say. Maybe you can get a bit slower GAL and get lucky. Cheers P #### petrus bitbyter Jan 1, 1970 0 matt said: I know that. No - the original chip was an 82S153 PLD, it's just that someone converted the contents of that to JEDEC format to work with a modern GAL (82S153's are hard to find and expensive). It worked for him, just can't figure out why it won't work for me. So perhaps I should buy and try a faster GAL? -15 perhaps? -10? -7? Maybe. But I'd be mistrust the conversion in the first place. Do you have the JEDEC of the original 82S153? If memory serves, AMAZE can convert the JEDEC back to logic equations so you can see what it is supposed to do. Once you know that you can edit the source for a GAL and get the right JEDEC for it. petrus bitbyter M #### matt Jan 1, 1970 0 Maybe. But I'd be mistrust the conversion in the first place. Do you have the JEDEC of the original 82S153? Afraid not, no. If memory serves, AMAZE can convert the JEDEC back to logic equations so you can see what it is supposed to do. The problem then, for me at least, is understanding them. Once you know that you can edit the source for a GAL and get the right JEDEC for it. So the equations would then be converted back to a JEDEC file? M #### matt Jan 1, 1970 0 Ah, pals and gals maybe I'll still get a chance to play with those. I would say you are most likely already way too fast, 250-300ns RAMs in those days, 82S153 probably had propagation delay of at least 40ns come to think of it it is not even PLD it is a PROM hence even larger propagation delay can be expected. A quick glance on goole, I don't see anythink with specs ( so many useless hits these days$#*%^& ) It is not in the "CMOS cook Book" must be in "TTL Cook Book" anybody have it handy?
Of the top of my head I don't even think it has an enable signal which you could .....
The old slow part may be bridging the time the inputs stop being valid and the outputs are read (since I don't believe the part has output enable),
the only way would be to buffer the outputs or use a device that could delay the outputs internaly.

Hmmm, thanks. Wish I could find a slower GAL! Do they still exist?
Why it worked for the other person (with same circuit, same speed and type GAL ) can't say. Maybe you can get a bit slower GAL and get lucky.

That's the problem - any ideas where from?

B

#### Ben Jackson

Jan 1, 1970
0
Something to do with the type of GAL or perhaps even the speed?

If the edge rate of the new GAL is too fast you could try putting 100
ohms or so inline with the new chip (build a small daughter card, perhaps).

But since you say it works for someone else, perhaps most likely is
that some other part of your 25 year old board is bad.

S

#### Sambo

Jan 1, 1970
0
matt said:
Hmmm, thanks. Wish I could find a slower GAL! Do they still exist?
Is it really everything identical as the other person is doing?
Even metal plate (grounded or not hmm) under the circuit could possibly make a difference.
Do you have the schematic? Converting to new pals, sounds like something I read a while ago with regard to fixing an old video game.
Sounds like you are programming the PAL yourself so you must be able to make a circuit board that would plug in place of the PAL and contain the new GAL 74??374 or 74??574 for the outputs and hex inverter to delay some clock signal . I maybe wrong and there is an enable input which you'd run through the inverters and to the clock of the ...... well this is already going in the wrong direction hehe.
Maybe it is more trouble than it is worth.
I could be done, but very difficult without deriving the timing from the board.

M

#### matt

Jan 1, 1970
0
If the edge rate of the new GAL is too fast you could try putting 100
ohms or so inline with the new chip (build a small daughter card, perhaps).

Would that just be on the outputs though?
But since you say it works for someone else, perhaps most likely is
that some other part of your 25 year old board is bad.

The board is okay as it works with the original 82S153 (which I can't
dump and don't have a replacement for - I'm testing the GAL on this
board but it will be going on another board (same type) as that one
has a bad 82S153).

I'm guessing that that guy who created the JEDEC file (a few years ago
now) used a slower GAL.

Thanks

M

#### matt

Jan 1, 1970
0
Is it really everything identical as the other person is doing?

Yup, except maybe he used a slower GAL? I don't know, just guessing.
Even metal plate (grounded or not hmm) under the circuit could possibly make a difference.

No, seems to be except the same I'm afraid.
Do you have the schematic? Converting to new pals, sounds like something I read a while ago with regard to fixing an old video game.

Yes, the schematic can be found here:

However, it's a 12MByte file as it's the complete manual - the schems
are towards the end of the PDF, you'll need to look at those for the
Memory Board. The device is question is the PLS at location U10

BTW, the quality of the schems is poor in places, but just about
Sounds like you are programming the PAL yourself

It's a GAL.
so you must be able to make a circuit board that would plug in place of the PAL and contain the new GAL 74??374 or 74??574 for the outputs and hex inverter to delay some clock signal .
I maybe wrong and there is an enable input which you'd run through the inverters and to the clock of the ...... well this is already going in the wrong direction hehe.
Maybe it is more trouble than it is worth.

Yes, maybe. Depends if it would work or not, and not sure if I could
do it without exact instruations on what to connect to what.
I could be done, but very difficult without deriving the timing from the board.

I see. Hmmmm, wish I could find a slower GAL.

Thanks

P

#### petrus bitbyter

Jan 1, 1970
0
matt said:
Afraid not, no.

The problem then, for me at least, is understanding them.

So the equations would then be converted back to a JEDEC file?

Sure, but JEDECs differ widely for different components. They often even
differ for the same component type but other manufacturer.

As for the speed itself I shouldn't expect problems. According to the
Philips datasheet the standard N82S153 is rated for 40ns, the N82S153A is
rated for 30ns. So your 25ns GAL may be too fast rather then too slow. But
in that case I consider it either a poor design or the use of some special
trick. Which will not help you, I'm afraid.

BTW It worked for someone else. Do you mean same board, same 82S143 content
and same object GAL? (So same type and brand?) Any idea what the GAL is
supposed to do? Any problem posting the JEDEC(s) you have? (Part of) the
schematic?

petrus bitbyter

M

#### matt

Jan 1, 1970
0
Sure, but JEDECs differ widely for different components. They often even
differ for the same component type but other manufacturer.

Really? Ugh - confusing!
As for the speed itself I shouldn't expect problems. According to the
Philips datasheet the standard N82S153 is rated for 40ns, the N82S153A is
rated for 30ns. So your 25ns GAL may be too fast rather then too slow. But
in that case I consider it either a poor design or the use of some special
trick. Which will not help you, I'm afraid.
:-((

BTW It worked for someone else. Do you mean same board,

Same board, yup (well, same design, same manufacturer, etc).
same 82S153 content
and same object GAL? (So same type and brand?)

Same GAL type: GAL16V8D - not sure what speed or brand he used though
as he's not replying to his emails.
Any idea what the GAL is
supposed to do?

I'll quote from the chap who came up with the JEDEC:

"All ROM and RAM on this Memory Board is initially decoded by the
82s153 FPLA at location U10. The FPLA enables address decoders based
on the upper 3 address bits of the address bus. Additionally, the FPLA
prevents ROM and RAM access during certain system processes including:
refresh cycles, active resets, I/O requests and a architecture
specific signal called /BUZOFF. The FPLA contains 5 address inputs and
7 status line inputs. Outputs of the FPLA are 4 decoder enable lines
and 1 transceiver direction select line. The enable line for ROMs X1
through X4 (74LS139 at U8, pin 1) is selected on addresses x0000-x3fff
( !a15, !a14). The 4 ROMs are then selected off of a13 and a 12 by the
lower half of the 139 decoder at U8. All the other selects work
similarly. The second half of U8 (pin 15, enable) selects ROMs X5-X8
(a15, !a14), the lower half of U9 (pin 1, enable) selects the ROMs at
X9 and X10 (a15, a14, !a13)and the upper half of U9 (pin 15 enable)
selects one of the 4 RAMs (a15, a14, a13) based on address lines a11
and a12).

The FPLA also selects the direction of the 74ls245 transceiver at U17.
On a write, pin 1 of U17 is held high to allow data to flow from the
processor data bus to the RAM/ROM board data bus, on a read the line
is held low and the data flows in the opposite direction. Most of the
additional circuitry on the ROM board deals with selecting the RAM at
X21 for high score and setup information. The three 74ls244s at U16,
U15 and U 11 are all used as line drivers with all of their select
lines tied low permanently.

The original FPLA used is a Signetics 82s153, which is now obsolete, a
modern replacement is a Signetics pls153, however I have not been able
to get a good copy of one so I had to write a replacement using a PLD
(GAL16V8D)."
Any problem posting the JEDEC(s) you have?

Here it is from the guy's site:

http://web.archive.org/web/20020331203553/http://my.erinet.com/~jamesm/tech/roto/roto.jed
(Part of) the
schematic?

I don't know how to extract a page or two from a PDF, but the whole
manual (12 MBytes! with schems at the end) can be found in this file:

http://arcarc.xmission.com/PDF Arcade Manuals and Schematics/Robby Roto.pdf

you'll need to look at the for the 'Memory Board'. The device in
question is the PLS at location U10

BTW, the quality of the schems is poor in places, but just about

Many thanks.

R

#### Rich Grise

Jan 1, 1970
0
I don't know how to extract a page or two from a PDF, but the whole
manual (12 MBytes! with schems at the end) can be found in this file:

You can draw a box around it, copy it to the clipboard, and paste it into
a paint program and save it as a .gif, then link to _that_.

Good Luck!
Rich

R

#### Rich Grise

Jan 1, 1970
0
The board is okay as it works with the original 82S153 (which I can't
dump and don't have a replacement for - I'm testing the GAL on this
board but it will be going on another board (same type) as that one
has a bad 82S153).

Can't dump it? Can't you plug it into a breadboard, put a counter on
the inputs, and see what you get at the outputs?

Then you would at least have a truth table, unless it's got some kind
of embedded state machine or something. It'd also help to know if
the outputs are latched or anything. Is there a data sheet anywhere
on the 82S153?

Good Luck!
Rich

M

#### matt

Jan 1, 1970
0
Can't dump it? Can't you plug it into a breadboard, put a counter on
the inputs, and see what you get at the outputs?

Only if I knew exactly what I was doing.
Then you would at least have a truth table, unless it's got some kind
of embedded state machine or something. It'd also help to know if
the outputs are latched or anything. Is there a data sheet anywhere
on the 82S153?

There's one here:

http://www.datasheetarchive.com/search.php?q=82s153&sType=part&ExactDS=Starts

Thanks for your help!

M

#### matt

Jan 1, 1970
0
You can draw a box around it, copy it to the clipboard, and paste it into
a paint program and save it as a .gif, then link to _that_.

Good point but I have no webspace - where would I upload it to?

S

#### Sambo

Jan 1, 1970
0
Ben said:
If the edge rate of the new GAL is too fast you could try putting 100
ohms or so inline with the new chip (build a small daughter card, perhaps).

But since you say it works for someone else, perhaps most likely is
that some other part of your 25 year old board is bad.

LOL, rotorooter? Let us know when you are fixing at least burger time hehe.

The most suspicious signal is the last (bottom) output controlling the U17
as someone suggested, resistor may work. Two transistor driver ( optionally with RC on input ) or run all outputs through 74L244 (L only, if it exists) although that only adds about 12ns, 'L' would probably be about 20ns.
I'd try the following, adding R1( and C1 only if needed, start in center position and reduce.

+5V ----------------------
| |
R1 |-| -
-------- 2.2K | | 510-1K | |
from PLA 13 ----| 1K |----| | | | |
-------- | T T
^ | 2.2K | |
| | --------- |/ ----- |/-----PPLA 13 socket
-------*-----| |----| |-------|
| --------- |\ |\
C1 | V V
100pf ===== | 2x2n4401 |
===== | |
| | |
| ===== =====
| === ===
=====
===

Or if using R1 C1 drop the second transistor with its resistor , put 1-1.5 K resistors
between collector and +5 and emitter and GND and take the signal from the emitter. However, this may not be a good idea for a digital circuit (slow rise time).

Now fire up that slow comp and it is time for a little Major Havoc, hehe.

Cheers.

M

#### matt

Jan 1, 1970
0
LOL, rotorooter?

Close - Robby roto in fact.
Let us know when you are fixing at least burger time hehe.
)

The most suspicious signal is the last (bottom) output controlling the U17
as someone suggested, resistor may work. Two transistor driver ( optionally with RC on input ) or run all outputs through 74L244 (L only, if it exists) although that only adds about 12ns, 'L' would probably be about 20ns.
I'd try the following, adding R1( and C1 only if needed, start in center position and reduce.

<snip>

Excellent, thanks - I'll make that up and let you know how it goes.

Cheers.

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