8 Dec
2007
8 Dec
'07
7:51 a.m.
Hi, all,
Has anyone here worked with or ever plotted silently to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count
rather aggresively,
since I'm going to hand-wire it.
One thought was to attempt to combine a 7490 _and_ a 7447 in a single
GAL16V8. I have blown hundreds of PALs, but have much less experience
in designing with them, so I'm not even sure that it's possible to mash
together that much logic internally in a 16V8. I know all the outputs
are optionally registered, so presuming one has 4 assignable flip-flops,
one could theoretically make a counter on the output pins, but what's
less clear to me is if you could then take those terms and internally
decode them to a 7-segment display.
After the large amounts of replies about this 8-way digital switch, I
don't necessarily want to clog the list with discissions of what is and
isn't possible for a GAL16V8, so if you can remember, please make any
suggestions and comments to me directly, not the list.
Thanks for any nudges towards a solution.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 8-Dec-2007 at 15:40 Z
South Pole Station
PSC 468 Box 400 Temp -25.4 F (-31.9 C) Windchill -52.5 F (-47.0 C)
APO AP 96598 Wind 13.7 kts Grid 12 Barometer 678.8 mb (10674 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
8 Dec
8 Dec
8:12 a.m.
On Sat, 8 Dec 2007, Ethan Dicks wrote:
Date: Sat, 8 Dec 2007 15:51:47 +0000
From: Ethan Dicks <ethan.dicks at usap.gov>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: cctalk at classiccmp.org
Subject: GAL16V8 as a modern substitute for a 7447?
Hi, all,
Has anyone here worked with or ever plotted silently to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count rather aggresively,
since I'm going to hand-wire it.
One thought was to attempt to combine a 7490 _and_ a 7447 in a single
GAL16V8. I have blown hundreds of PALs, but have much less experience
in designing with them, so I'm not even sure that it's possible to mash
together that much logic internally in a 16V8. I know all the outputs
are optionally registered, so presuming one has 4 assignable flip-flops,
one could theoretically make a counter on the output pins, but what's
less clear to me is if you could then take those terms and internally
decode them to a 7-segment display.
After the large amounts of replies about this 8-way digital switch, I
don't necessarily want to clog the list with discissions of what is and
isn't possible for a GAL16V8, so if you can remember, please make any
suggestions and comments to me directly, not the list.
Thanks for any nudges towards a solution.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 8-Dec-2007 at 15:40 Z
South Pole Station
PSC 468 Box 400 Temp -25.4 F (-31.9 C) Windchill -52.5 F (-47.0 C)
APO AP 96598 Wind 13.7 kts Grid 12 Barometer 678.8 mb (10674 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
IICRC the 16V8 does not have buried registers so you will lose the 4 of the
output pins (for the counter) that you needed for the 7 segment outputs
If you are using sockets, a 5V or 3.3V (cheaper) 44 pin PLCC CPLD might be a
better solution, plus they are easier to program. A X9572XL will probably do 4
decades of count/decode for about $2.00
Peter Wallace
Mesa Electronics
(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.
10:30 a.m.
On Sat, Dec 08, 2007 at 08:12:30AM -0800, Peter C. Wallace wrote:
On Sat, 8 Dec 2007, Ethan Dicks wrote:
Right.
Has anyone here worked with or ever plotted
silently to create a moderish
7-segment decoder/driver from a GAL16V8?
IICRC the 16V8 does not have buried registers so you will lose the 4 of the
output pins (for the counter) that you needed for the 7 segment outputs If you are using sockets, a 5V or 3.3V (cheaper) 44
pin PLCC CPLD might be
a better solution, plus they are easier to program. A X9572XL will probably
do 4 decades of count/decode for about $2.00
That is not feasible. I need 7 or 9 decades of count/decode, and I happen
to have an abundance of GALs and a GAL programmer. If it comes down to a
CPLD-design, I'll probably throw in the towel and use an AVR microcontroller
and perhaps a real 74LS47 or 74LS247 to lower the I/O requirements a touch.
I was just musing about what it might take to put it all in hardware
rather than a combination of hardware and firmware. Using an MCU makes
the entire problem trivial.
Thanks,
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 8-Dec-2007 at 18:20 Z
South Pole Station
PSC 468 Box 400 Temp -25.2 F (-31.8 C) Windchill -52.6 F (-47.0 C)
APO AP 96598 Wind 14.0 kts Grid 20 Barometer 678.3 mb (10692 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
9:42 a.m.
Ethan Dicks wrote:
Has anyone here worked with or ever plotted silently
to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count rather aggresively,
since I'm going to hand-wire it.
One thought was to attempt to combine a 7490 _and_ a 7447 in a single
GAL16V8. I have blown hundreds of PALs, but have much less experience
Do you need the driver to count?
I would decode the input and latch the outputs for the display
if you did not need a count.
Thanks for any nudges towards a solution.
-ethan
1:29 p.m.
Date: Sat, 8 Dec 2007 10:42:00 -0700
From: bfranchuk at jetnet.ab.ca
To:
Subject: Re: GAL16V8 as a modern substitute for a 7447?
Ethan Dicks wrote:
Hi
There is no reason that the counter has to be binary. I think there
are enough terms to do a 7 segement count using the output latches.
Load would require a binary to 7 segment decode. Just decode
in front of the strange counter.
Just thinking out side of the box.
Dwight
_________________________________________________________________
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Has anyone here worked with or ever plotted
silently to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count rather aggresively,
since I'm going to hand-wire it.
One thought was to attempt to combine a 7490 _and_ a 7447 in a single
GAL16V8. I have blown hundreds of PALs, but have much less experience
Do you need the driver to count?
I would decode the input and latch the outputs for the display
if you did not need a count.
Thanks for any nudges towards a solution.
-ethan
1:46 p.m.
From: dkelvey at hotmail.com
Hi
There is no reason that the counter has to be binary. I think there
are enough terms to do a 7 segement count using the output latches.
Load would require a binary to 7 segment decode. Just decode
in front of the strange counter.
Just thinking out side of the box.
Dwight
Oops, it looks like several other have also suggested
this.
Dwight
_________________________________________________________________
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8 Dec
8 Dec
10:08 a.m.
Ethan wrote
Has anyone here worked with or ever plotted silently
to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count rather aggresively,
since I'm going to hand-wire it.
I have build a small clock, and did not want to do much wiring,
so I used 73LS390 and those fancy HP "7-segment" displays
that display the numbers in a series of dots. Old HP counters have them.
I love those displays. Also, those displays have a 4-bit latch and "7447"
incorporated. They have 4 (or 5, I can't remember) pins on the lower
side and ditto on the upper side. 4 pins are obviously for the BCD code,
2 pins are for +5V power supply, one pin is LATCH, one pin is BLANK.
The dimensioning is such that they can be "stacked", put neatly next to
each other. As these displays have the 7-segment decoder and the BCD latch
inside, it made the wiring/soldering quite easy, and you get a "cool display"
:-)
Henk
10:17 a.m.
On Sat, Dec 08, 2007 at 07:08:29PM +0100, Henk Gooijen wrote:
Ethan wrote
It sounds like you are describing the TIL311. They are very nice. I
have a number of them (with me here) and have worked with them since
my first Elf in the late 1970s. Unfortunately, for what I am trying to
do, they aren't my first choice - I have an existing mechanical spacing
that I'm trying to stay compatible with, and it's too wide for a reasonable
bank of TIL311s.
Has anyone here worked with or ever plotted
silently to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts...
I have build a small clock, and did not want to do much wiring,
so I used 73LS390 and those fancy HP "7-segment" displays
that display the numbers in a series of dots. Old HP counters have them. The dimensioning is such that they can be
"stacked", put neatly next to
each other. As these displays have the 7-segment decoder and the BCD latch
inside, it made the wiring/soldering quite easy, and you get a "cool display"
:-)
They do stack nicely, and they do make a cool display. Unfortunately, I
need something that's about 0.2" wider than a TIL311, and that happens to
be some HP 7-segment displays, which is why I asked about the 7447 rather
than going off and doing my own thing with TIL311s.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 8-Dec-2007 at 18:10 Z
South Pole Station
PSC 468 Box 400 Temp -25.2 F (-31.8 C) Windchill -52.1 F (-46.7 C)
APO AP 96598 Wind 13.4 kts Grid 9 Barometer 678.4 mb (10689 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
10:33 a.m.
Ethan Dicks [ethan.dicks at usap.gov] wrote:
Thanks for any nudges towards a solution.
Implementing the combinatorial logic for a seven segment decoder is
trivial even for the simplest GAL. But, as somebody else pointed out, the
latches in a simple GAL are permanently tied to output pins, so a 4 bit
counter plus a seven segment decoder would need 4+7=11 output pins. A 16V8
has only 8 outputs, and a 22V10 has only 10, which rules both of them out.
Now if you only wanted it to latch the data rather than count, that'd be
possible with a 16V8.
Hmm... Having said all that, it might be possible to put a state machine
into a 16V8 that had a 7 bit current state and a next state function that
corresponded to "counting" is seven segments. In theory that'd work, but I
don't know off hand if there are enough terms inside a 16V8 to implement
that next state function. I'll leave that as an exercise for the reader :-)
Another thing to keep in mind is that parts like these are really power
hungry, even compared with traditional 74xx parts.
Ethan Dicks, A-333-S Current South Pole Weather at
8-Dec-2007 at
15:40 Z
Are you back down there again?? Did you see the NBC news team that
visited a few weeks ago?
Bob
10:41 a.m.
On Sat, Dec 08, 2007 at 10:33:23AM -0800, Bob Armstrong wrote:
Right.
Ethan Dicks
[ethan.dicks at usap.gov] wrote:
Thanks for any nudges towards a solution.
Implementing the combinatorial logic for a seven segment decoder is
trivial even for the simplest GAL. But, as somebody else pointed out, the
latches in a simple GAL are permanently tied to output pins, so a 4 bit
counter plus a seven segment decoder would need 4+7=11 output pins. A 16V8
has only 8 outputs, and a 22V10 has only 10, which rules both of them out. Now if you only wanted it to latch the data rather
than count, that'd be
possible with a 16V8.
I could get away with an external counter easily enough, but I was
musing aloud about a way to cut the part-count in half.
Hmm... Having said all that, it might be possible
to put a state machine
into a 16V8 that had a 7 bit current state and a next state function that
corresponded to "counting" is seven segments. In theory that'd work, but
I
don't know off hand if there are enough terms inside a 16V8 to implement
that next state function. I'll leave that as an exercise for the reader :-)
Indeed. Someone else already made that suggestion, and I'm thinking
about it. The good news is that it's easy to prototype one up and
see how it works on a breadboard.
Another thing to keep in mind is that parts like
these are really power
hungry, even compared with traditional 74xx parts.
True. Power is not really an issue here. The LEDs are going to pull
a fair amount of power on their own, not including counting and driving.
Are you back down there again?? Did you see the NBC
news team that
visited a few weeks ago?
Yep... I arrived back here about 5 weeks ago. I did see the NBC crew
on their brief stop-over, including Ann Curry making a bit of fun of
our soft-serve ice-cream machine (they arrived around 01:00 and departed
around 03:00, and I happened to be up when they arrived).
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 8-Dec-2007 at 18:30 Z
South Pole Station
PSC 468 Box 400 Temp -25.2 F (-31.8 C) Windchill -53.8 F (-47.6 C)
APO AP 96598 Wind 15.5 kts Grid 12 Barometer 678.3 mb (10692 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
7:21 p.m.
The good news is that it's easy to prototype one up
and
see how it works on a breadboard.
Breadboard? As in hardware? That's for sissies - we have simulators now
:-)
FWIW, I tried it and it is possible to fit a decimal counter with seven
segment outputs, a carry out, and a synchronous clear into a single 16V8.
Hint: you have to invert one of the state machine bits, and then invert the
corresponding output pin, but if you do that it'll fit.
You didn't say whether you need a parallel load (in BCD, presumably) too -
that'd almost certainly be too many AND terms.
True. Power is not really an issue here. The LEDs are
going to pull
a fair amount of power on their own, not including counting and driving.
A 16V8 can use 100mA or so. How many decades did you say you wanted?
That's gonna add up fast...
Bob
8 Dec
8 Dec
3:48 p.m.
Hmm... Having said all that, it might be possible to
put a state
machine into a 16V8 that had a 7 bit current state and a next state
function that corresponded to "counting" is seven segments. In
theory that'd work, but I don't know off hand if there are enough
terms inside a 16V8 to implement that next state function.
You also need to make sure that the next-state function converges on a
valid state from all possible start states, or else add a way to reset
it to some valid state (probably zero).
Using (what I think of as) the canonical 7-stroke digits,
_ _ _ _ _ _ _ _
| | | _| _| |_| |_ |_ | |_| |_|
|_| | |_ _| | _| |_| | |_| _|
with the segments identified as A to G from top to bottom, left to
right, the digits are
A B C D E F G
0 1 1 1 0 1 1 1
1 0 0 1 0 0 1 0
2 1 0 1 1 1 0 1
3 1 0 1 1 0 1 1
4 0 1 1 1 0 1 0
5 1 1 0 1 0 1 1
6 1 1 0 1 1 1 1
7 1 0 1 0 0 1 0
8 1 1 1 1 1 1 1
9 1 1 1 1 0 1 1
Then, if X' is the next-state X, I find that, optimizing for gate count
(NOT, AND, OR, NAND, NOR), if I didn't make any typos feeding the
program,
A' = ~(G&F&~(D&B)) [2 gates - 2NAND, 3NAND]
B' = (C&F&D)|(A&~E) [4 gates - NOT, 2AND, 3AND, 2OR]
C' = E|~(B&~(D&C&A&B)) [3 gates - 4NAND, 2NAND, 2OR]
D' = ~(B&(C|E)&A&~(D&C&F&E)) [3 gates - 4NAND, 2OR, 4NAND]
E' = ~(E|(D&~(D&A&B))) [3 gates - 3NAND, 2AND, 2NOR]
F' = A|D [1 gate - 2OR]
G' = ~(G&F&(C|E)&~(D&C&A&B)) [3 gates - 4NAND, 2OR, 4NAND]
There's even a little commonality; ~(D&C&A&B) and (C|E) each occur
twice. (Trying to optimize for total gate count over all seven signals
would have been a lot more computation, using the technique I used.)
If this gate-count metric is not appropriate for a GAL, outline a more
appropriate metric and I can work out equations using it....
Using these equations, I find that, fortunately, all 128 initial states
settle into one of the ten digits in no more than four transitions, and
even that many for only six of the 128: 0101000, 0101001, 0101010,
0101011, 0111000, and 0111001. Interestingly, the digit all six of
those turn into after four transitions is the same. ("Fortunately"
because the way I did this doesn't have any good way to feed
information back into the equation determination from the loop
detection.)
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse at rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
9 Dec
9 Dec
1:03 p.m.
Hmm... Having said all that, it might be
possible to put a state
machine into a 16V8 that had a 7 bit current state and a next state
function that corresponded to "counting" is seven segments. In
theory that'd work, but I don't know off hand if there are enough
terms inside a 16V8 to implement that next state function.
You also need to make sure that the next-state function converges on a
valid state from all possible start states, or else add a way to reset
it to some valid state (probably zero).
Using (what I think of as) the canonical 7-stroke digits,
_ _ _ _ _ _ _ _
| | | _| _| |_| |_ |_ | |_| |_|
|_| | |_ _| | _| |_| | |_| _|
with the segments identified as A to G from top to bottom, left to
right, the digits are
A B C D E F G
0 1 1 1 0 1 1 1
1 0 0 1 0 0 1 0
2 1 0 1 1 1 0 1
3 1 0 1 1 0 1 1
4 0 1 1 1 0 1 0
5 1 1 0 1 0 1 1
6 1 1 0 1 1 1 1
7 1 0 1 0 0 1 0
8 1 1 1 1 1 1 1
9 1 1 1 1 0 1 1
Then, if X' is the next-state X, I find that, optimizing for gate count
(NOT, AND, OR, NAND, NOR), if I didn't make any typos feeding the
program,
A' = ~(G&F&~(D&B)) [2 gates - 2NAND, 3NAND]
B' = (C&F&D)|(A&~E) [4 gates - NOT, 2AND, 3AND, 2OR]
C' = E|~(B&~(D&C&A&B)) [3 gates - 4NAND, 2NAND, 2OR]
D' = ~(B&(C|E)&A&~(D&C&F&E)) [3 gates - 4NAND, 2OR, 4NAND]
E' = ~(E|(D&~(D&A&B))) [3 gates - 3NAND, 2AND, 2NOR]
F' = A|D [1 gate - 2OR]
G' = ~(G&F&(C|E)&~(D&C&A&B)) [3 gates - 4NAND, 2OR, 4NAND]
The structure of a PAL/CAL is a programmable AND matrix followed by a
fixed OR matrize. That is, the D inputs of the flip-flops come from OR
gates (with, a fixed number of inputs, I think 8 in this case), the inputs
of thost OR gates come from AND gates which can be programmed to AND
together any comination of inputs, feedback terms (outputs of the
flip-flops) and their inverses. With a GAL (although not a PAL), you can
invert the final output on the pin (that is, make the D-tupe store A'
rather than A) if it manas the logic will fit), but IIRC, you have to keep
track of whether each flip-flop is inverted or not, since you have to use
the right sense of the feedback terms. Some CAD tools with convert
arbitrary equations into the right SOP form, sometimes you get to do it
yourself.
-tony
1:53 p.m.
Hmm... Having said all that, it might be
possible to put a state
machine into a 16V8 that had a 7 bit current state and a next state
function that corresponded to "counting" is seven segments. In
theory that'd work, but I don't know off hand if there are enough
terms inside a 16V8 to implement that next state function.
You also need to make sure that the next-state function converges on a
valid state from all possible start states, or else add a way to reset
it to some valid state (probably zero).
Using (what I think of as) the canonical 7-stroke digits,
_ _ _ _ _ _ _ _
| | | _| _| |_| |_ |_ | |_| |_|
|_| | |_ _| | _| |_| | |_| _|
with the segments identified as A to G from top to bottom, left to
right, the digits are
A B C D E F G
0 1 1 1 0 1 1 1
1 0 0 1 0 0 1 0
2 1 0 1 1 1 0 1
3 1 0 1 1 0 1 1
4 0 1 1 1 0 1 0
5 1 1 0 1 0 1 1
6 1 1 0 1 1 1 1
7 1 0 1 0 0 1 0
8 1 1 1 1 1 1 1
9 1 1 1 1 0 1 1
Then, if X' is the next-state X, I find that, optimizing for gate count
(NOT, AND, OR, NAND, NOR), if I didn't make any typos feeding the
program,
A' = ~(G&F&~(D&B)) [2 gates - 2NAND, 3NAND]
B' = (C&F&D)|(A&~E) [4 gates - NOT, 2AND, 3AND, 2OR]
C' = E|~(B&~(D&C&A&B)) [3 gates - 4NAND, 2NAND, 2OR]
D' = ~(B&(C|E)&A&~(D&C&F&E)) [3 gates - 4NAND, 2OR, 4NAND]
E' = ~(E|(D&~(D&A&B))) [3 gates - 3NAND, 2AND, 2NOR]
F' = A|D [1 gate - 2OR]
G' = ~(G&F&(C|E)&~(D&C&A&B)) [3 gates - 4NAND, 2OR, 4NAND]
The structure of a PAL/CAL is a programmable AND matrix followed by a
fixed OR matrize. That is, the D inputs of the flip-flops come from OR
gates (with, a fixed number of inputs, I think 8 in this case), the inputs
of thost OR gates come from AND gates which can be programmed to AND
together any comination of inputs, feedback terms (outputs of the
flip-flops) and their inverses. With a GAL (although not a PAL), you can
invert the final output on the pin (that is, make the D-tupe store A'
rather than A) if it manas the logic will fit), but IIRC, you have to keep
track of whether each flip-flop is inverted or not, since you have to use
the right sense of the feedback terms. Some CAD tools with convert
arbitrary equations into the right SOP form, sometimes you get to do it
yourself.
-tony
7 Mar
7 Mar
8:03 a.m.
New subject: Test software for PANDA display?
Hi, Bob,
I'm finally nearing completion of my Panda display, at last, and I
rememeber another Panda display owner mentioning that you sent them
a test program to cycle the LEDs. Could you send that to me? I'm
using Linux, so I'd prefer C or C++ source than a compiled binary,
if that's OK (I've been twiddling LEDs and such from the parallel
port under Linux for a while, so I don't anticipate any problems
if I have to massage the code; of course you'd be welcome to any
changes I made).
I didn't get a chance to place a last parts order before the last
plane, so I'm improvising like mad here. I found a couple of 4.7K
SIPs (one just yesterday, thus the progress), but I may have to
use discretes for the LED current limiters. To help me in my search,
what values are reasonable for RP1-RP5 and RP8? I think I can find
a wad of 220 Ohm resistors, but other low values might or might not
be present here in the necessary abundance.
Thanks,
-ethan
P.S. - I do have the JEDEC file for the GAL, a programmer, and several
blanks, so that's no problem - just the current limiters.
--
Ethan Dicks, A-333-S Current South Pole Weather at 7-Mar-2008 at 15:50 Z
South Pole Station
PSC 468 Box 400 Temp -45.2 F (-42.9 C) Windchill -82.5 F (-63.6 C)
APO AP 96598 Wind 18.8 kts Grid 35 Barometer 680.0 mb (10628 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
8:19 a.m.
New subject: Test software for PANDA display?
On Fri, Mar 07, 2008 at 04:03:54PM +0000, Ethan Dicks wrote:
I'm finally nearing completion of my Panda
display...
Oops... that was meant to be off-list. Sorry.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 7-Mar-2008 at 16:10 Z
South Pole Station
PSC 468 Box 400 Temp -45.0 F (-42.8 C) Windchill -79.5 F (-61.9 C)
APO AP 96598 Wind 15.5 kts Grid 32 Barometer 680.1 mb (10624 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
8 Dec
8 Dec
12:17 p.m.
At 06:51 AM 12/8/2007, you wrote:
Hi, all,
Has anyone here worked with or ever plotted silently to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count rather aggresively,
since I'm going to hand-wire it.
Look at the 750 SPLD from atmel. Its 28 pins and has a lot more
internal stuff than a regular 22V10.
3:01 p.m.
Hi, all,
Has anyone here worked with or ever plotted silently to create a moderish
7-segment decoder/driver from a GAL16V8? I'm working on a project made
from classic parts, and am trying to reduce part count rather aggresively,
since I'm going to hand-wire it.
One thought was to attempt to combine a 7490 _and_ a 7447 in a single
GAL16V8. I have blown hundreds of PALs, but have much less experience
in designing with them, so I'm not even sure that it's possible to mash
together that much logic internally in a 16V8. I know all the outputs
are optionally registered, so presuming one has 4 assignable flip-flops,
one could theoretically make a counter on the output pins, but what's
less clear to me is if you could then take those terms and internally
decode them to a 7-segment display.
I'm pretty sure you can't.
Yes, you can sue 4 of the flip-flips to make a counter (although with a
common clock input, you would have to make a synchronous counter, and
I've not worked out if you have enough product terms to do that, I think
you do, thought). But those 4 flip-flops take up 4 of the 8 outputs of
your GAL.
Yes, you can use feedback terms to process the otuputs of that counter.
But you only havr 4 outputs left, and you need 7 for drive a 7-segment
display.
What I've not workeod out if you can do (and I suspect you don't ahve
enough product terms to do it) is to make a state machine with 7
flip-flops, the 10 allowed states of which are the 7 segment patterns,
and a trasnition table something like :
1111110 -> 0110000 -> 1101101 etc
0 1 2 (7 segemnt patterns)
I suepect you don't have enough product terms to do that, but I have not
tried to work it out.
-tony
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