Well that did it Bob. I have improved things as well. Because I want this
Toggle bit to reset to a defined state upon reset, I managed to allow the
TOGOUT to always be high upon reset and to then toggle high/low with each port
input.
Great, this saves me using one 74LS74 chip on this S100 80486 board I’m
building where every extra chip takes up precious real estate.
Here is the PALASM code in case anybody need this later:-
;---------------------------------- PIN Declarations ---------------
PIN 1 PULSE_IN ;CLK pin, input from pin 23 (PULSE_OUT)
PIN 2 A0 ;Note these are actual S100 bus address lines
(outside the 80386)
PIN 3 A1
PIN 4 A2
PIN 5 A3
PIN 6 A4
PIN 7 A5
PIN 8 A6
PIN 9 A7
PIN 10 A8
PIN 11 A9
Pin 12 GND
Pin 13 A10
Pin 14 A11
Pin 15 A12
Pin 16 A13
Pin 17 A14
Pin 18 A15
Pin 19 sINP ;S100 bus status Port IN line
Pin 20 pDBIN ;S100 bus port write
Pin 21 /RESET ;Active pulse LOW
Pin 22 TOGOUT
Pin 23 PULSE_OUT ;Pulse to clock pin 1 input
;----------------------------------- Boolean Equation Segment ------
EQUATIONS
/PULSE_OUT = A0 * /A1 * A2 * A3 * /A4 * A5 * A6 * A7 ;Port
EDH = 1110 1101
* /A8 * /A9 * /A10 * /A11 * /A12 * /A13 * /A14 * /A15
* sINP * pDBIN
+ RESET * TOGOUT ;Clock
LOW if HIGH with reset
TOGOUT := /TOGOUT * /RESET ;Toggle
+ RESET
Thanks Bob for the help
John
From: [email protected] [mailto:[email protected]] On
Behalf Of Bob Bell
Sent: Wednesday, February 18, 2015 6:49 PM
To: [email protected]
Subject: RE: [N8VEM-S100:6345] Need help with a simple GAL programming problem.
We’re half-way…
The output from GAL pin 22 needs to connect to the GAL pin 1. Then every time
you output to port 00EDh, you will get a pulse on pin 22. You already have
this and the equation to do it. This is now the clock to another cell in the
GAL via pin 1. Let’s say you use the cell on pin 21 for this. The PALASM for
this cell is simply to clock the inverted cell output to the output, just like
the D F-F does. Assuming you name pin 21 TOGOUT, I think the equation for this
is simply:
TOGOUT = /TOGOUT
You have to tell the GAL that the pin 21 cell is registered so it connects the
F-F and pulls the clock from pin 1. I’m not altogether sure how that’s done or
if there is some dependency on the programmer you’re using.
Bob Bell
From: [email protected] [mailto:[email protected]] On
Behalf Of John Monahan
Sent: Wednesday, February 18, 2015 9:41 PM
To: [email protected]
Subject: RE: [N8VEM-S100:6344] Need help with a simple GAL programming problem.
If I understand you correctly then Bob you would have to input from the port
twice ? First to setup the output (low to high on pin 21), then AGAIN on
another output pin (say pin 22) which would be connected to the CLK pin1.
This would clock the register from the first output. That output would fee into
pin 23 so it can be inverted next time.
If I have this correct, it’s not really what I want. I need one input from the
port to toggle. Otherwise I have to backtrack on old software.
If I have it wrong could you supply PALASM code and/or a diagram. I’m
attaching the current schematic. I would like to eliminate the need for the
74LS74.
Thanks
John
From: [email protected] [mailto:[email protected]] On
Behalf Of Bob Bell
Sent: Wednesday, February 18, 2015 6:17 PM
To: [email protected]
Subject: RE: [N8VEM-S100:6343] Need help with a simple GAL programming problem.
John,
I’m just beginning to get into programming GALs for an S-100 memory board I’m
designing (or I should say re-designing), and I have been doing a lot of
research. In the 80’s, I used PALASM to program PALs on a regular basis, so my
need to learn GAL programming is awakening many old memories.
If I understand you correctly, you want a GAL output to start low (upon some
reset or power-up I presume), then on an input from port 00EDh, you want it to
go high and stay high. Then on a subsequent port input, you want it to go back
low and stay low. As I see it, this is a simple divide by two circuit. If I
was implementing it with a D flip-flop, I would simply tie the /Q output pin
back to D input and then clock the flip flop with the output of the port
detection logic. Assuming you want a known state on power-up or reset, I would
connect the D flip-flop’s /Reset input to /POR.
So, for your GAL, you’ll need a registered output. Since a 22V10 has a single,
common clock input, and cannot come from the matrix or a GAL output internally,
you’ll need to tie that to another output that has implemented your port
detection logic as you have written. Then each time you write to that port,
the GAL combinatorial logic will pulse its output and be fed back to the clock
input, clocking the register cell that you will setup. Your port detection
logic looks correct to me. This would be the combinatorial output that you
will wire to the GAL CLK input. Then you need to add an equation for the
registered cell that uses the output of the register, internally, to set the
register output either low or high depending on the state of the register
output feedback. This will implement the toggle function you are looking for.
That would look something like this I think:
TogOut = /TogOut
So, I think you have enough pins. The output of the port detection logic can
be pin 23. This is hard-wired externally to the GAL to pin 1. Since the
register output can feedback internally, it does not use a pin. That leaves
pin 22 for your reset if you want to implement that.
I know this is not thought out 100%, but I hope it’s enough to help you get
going.
Bob Bell
From: [email protected] [mailto:[email protected]] On
Behalf Of monahanz
Sent: Wednesday, February 18, 2015 7:59 PM
To: [email protected]
Subject: [N8VEM-S100:6342] Need help with a simple GAL programming problem.
Could anybody out there that remembers programming GAL's (specifically the 24
pin 22V10 variety), help me on what I'm sure is a simple problem.
I want the GAL to topple low to high on a port input. and stay high., The next
time on a port input toggle back high to low and stay low. In other words
inputting from a port toggles the output. I'm a bit limited with pins
available, only 3:-
PIN 1 NC
PIN 2 A0 ;Note these are actual S100 bus address
lines (outside the 80386)
PIN 3 A1
PIN 4 A2
PIN 5 A3
PIN 6 A4
PIN 7 A5
PIN 8 A6
PIN 9 A7
PIN 10 A8
PIN 11 A9
Pin 12 GND
Pin 13 A10
Pin 14 A11
Pin 15 A12
Pin 16 A13
Pin 17 A14
Pin 18 A15
Pin 19 sINP ;S100 bus status Port IN line
Pin 20 pDBIN ;S100 bus port read
Pin 21 TOGGLE_OUTPUT
Pin 22 NC
Pin 23 NC
;----------------------------------- Boolean Equation Segment ------
EQUATIONS
TOGGLE_OUTPUT = A0 * /A1 * A2 * A3 * /A4 * A5 * A6 * A7
;EDH = 1110 1101
* /A8 * /A9 * /A10 * /A11 * /A12 * /A13
* /A14 * /A15
* sINP * pDBIN
;Activate board with Z80 monitor QIED
command
I'm assuming I need a register output, not sure what the clock should be. Any
suggestions as to a layout.
John
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