need info on anti-static measures when working with basics stamps.
allie
Posts: 109
Hi to all.
I'm new to basic stamps. I have the basic stamp 2 module with the Super Carrier Board. I'm use to working with the standard·TTL logic chips but not static sensitives devices. My question is, while in the development stage with out any power to the board would it·help to put the board into a shallow tin pan(grounded to a ground rod)? Should the pan where it grounds have a resistor hooked to it in series with the ground rod? I have an anti-static wrist strap, but is it over kill to use the grounded pan? I plan to invest in a,·on top of the·work bench anti-static matt. Does any·one know·of·a good place where I can·buy one for the hobbiest budget?
Also, I plan to try to interface the basic stamp 2 to one of the older commodore 64's computers user interface port. The 64's ports specs. say I/O pins have passive pull up devices as well as active pull-ups, providing both CMOS and TTL compatibility. I/O pins have two TTL load drive capability. My math figures this to be around 1.8ma+1.8ma(a fan out of 2 for TTL) which = 3.6ma per I/O pin. Question; How can it be compatibility with CMOS and TTL at the same time? I'm not sure what they mean by passive pull-up devices as well as active pull-ups. I think it means resistors pulling up to +5 volts. Question; meaning of passive and meaning of active in this context. Question; Should it be o.k. to interface the 64 to the basic stamp 2.
Thanks in advance.
Regards allie
I'm new to basic stamps. I have the basic stamp 2 module with the Super Carrier Board. I'm use to working with the standard·TTL logic chips but not static sensitives devices. My question is, while in the development stage with out any power to the board would it·help to put the board into a shallow tin pan(grounded to a ground rod)? Should the pan where it grounds have a resistor hooked to it in series with the ground rod? I have an anti-static wrist strap, but is it over kill to use the grounded pan? I plan to invest in a,·on top of the·work bench anti-static matt. Does any·one know·of·a good place where I can·buy one for the hobbiest budget?
Also, I plan to try to interface the basic stamp 2 to one of the older commodore 64's computers user interface port. The 64's ports specs. say I/O pins have passive pull up devices as well as active pull-ups, providing both CMOS and TTL compatibility. I/O pins have two TTL load drive capability. My math figures this to be around 1.8ma+1.8ma(a fan out of 2 for TTL) which = 3.6ma per I/O pin. Question; How can it be compatibility with CMOS and TTL at the same time? I'm not sure what they mean by passive pull-up devices as well as active pull-ups. I think it means resistors pulling up to +5 volts. Question; meaning of passive and meaning of active in this context. Question; Should it be o.k. to interface the 64 to the basic stamp 2.
Thanks in advance.
Regards allie
Comments
This has been a reoccuring question. You might get a lot of benefit from using the Search.
In a nutshell, static electricity is a problem. But being grounded in the wrong way might put you in the hospital or worse. Generally all grounding for static electricty should go through something like a 1 meg resistor to limit how much of a Zap a person might take.
Simply touching a ground before getting to work is often a better, safer, and saner solution than getting tangle up with a live circuit. Usually once devices are in circuit, static electrical damage is much less of a problem.
Pull-up's can be Active [noparse][[/noparse]use transistors] or Passive [noparse][[/noparse]use resistors]. The Passive or resistors tend to slow down the responsiveness of the system, but allow for an open bus architecture.
I have a bit of trouble understanding why the Commodore would try to feature both; but it· was a long time ago. Try to identify the actual chips that drive the output. ·4000 series CMOS are not as robust as later generations and you need to know what the quirks of what you have are.
There is some overlap between the CMOS and TTL logic range, but I believe that TTLs will withstand a higher voltage.
'The Art of Electronics' discusses the differences and how to mate nearly all the generations of chips to each other without having problems. And it includes a good explanation of proper us of pull-ups.
BasicStamps are basically good for 20ma or more sink or source on one pin. They seem to be collectively rated at One Watt, which means that pushing 200ma @ 5 or less through them is doable. Over that and you have to expect smoke, sparks, and general chaos.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
Post Edited (Kramer) : 2/19/2006 3:12:08 PM GMT
Thanks again
regards
allie
·· Now there's an Old-School chip.· MOS Tech hasn't been in business for many years.· May I ask why you're trying to use this older chip?· There may be a much better solution for the BASIC Stamp, which wasn't really designed for these types of chips.· I'm not saying it couldn't be done, but these chips were designed to interface with a CPU not an MCU.· CPUs have an address bus, data bus and control bus.· MCUs have that internal and the I/O external.· If you need more I/O that can be easily done using a lot less pins using shift registers.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
Good question.
I'm designing an interface to control 4 five volt relays. I have an older commodore 64 computer which has a friendly user port for connecting to external circuits. I like the commodore 64 because I can program in the basic language. I'm looking to control 4 stepper motors with only 2 stepper motor controllers ***sherline lath & milling machine***. This is where the 4 relays come in. The commodore 64 can handle this quite well as can also display results to the screen for a lot of information. I also want to interface the basic stamp 2 into this to take over in the event that the 64 malfunctions. ***64's are getting very old but repair shops are still keeping them up and running. I know that the basic stamps can handle this alone but with the combination of both the 64 and the basic stamps, there is a powerful design system.
I'm sure I'll want the commodore 64 and the basic stamp to interface with each other at some point. So I want to learn as much as I can before I try.
My commodore 64 interfacing books say that the commodore 64's user port can interface directly to an 7404 hex inverter also 74LS174, 74LS374 and 74LS85 for outputs. It also shows the MC1489 receiver chip interfaced as an input to the 64 for rs232 conversions back to ttl levels. There is also a CMOS NOR gate (74C02) connected to the I/O ports for input.
The interfacing book says that the 64 and the 7400 series ICs both use the same logic system of a 1 represented by 2.6 to 5 volts and a 0 by 0 to .6 volts. The book also says that the 6526 interface chip I/O lines are pulled up to +5 volts by 10,000 ohm resistors inside the 6526 chip.
Commodore 64's game port's use a second 6526 chip (same kind) as I/O chip mentioned above. The joysticks just short the input pins to ground. When joysticks input switches are opened the internal 10,000 ohm resistors pull up the input pins to +5volts.
Question; Can the basic stamp 2 interface to the 64's I/O pins directly?
The only difference that I see is the stamp can source up to 20ma if only 2 pins used per group and the 64 can source 2 TTL level loads of 3.6ma. If I wired them pin for pin would I need resistors and what value.
Thanks for the reply.
Regards allie
Back to your static concerns: A reasonably priced conductive mat can be found here, but there are many other sources:· http://www.elexp.com/ant_asw1.htm
·With ESD precautions, being careful but not paranoid is the way to go. Basic ESD procedures when components are out of circuit are called for, such as when handling devices during installation, or when you've been scuffling around on carpet with a sweater on, etc., (even when they are installed in circuit.) I agree with Kramer that they are much less susceptible, but not insusceptible, when in circuit. Otherwise, Parallax wouldn't package most of their devices in antistatic bags. You can make a faraday cage with tinfoil to store large boards, but make sure they don't have any batteries installed!
A good discussion of reasonable practices can be found here:
http://www.radio-electronics.com/info/circuits/esd/esd_protection.php
Hope it helps,
Jim
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
In the end, it seems that it's all about getting the LEDs to blink....
·· My original computer business started with the VIC-20 and C=64.· I spent 15 years working with these machines, and if I still lived where I was when I started I would probably still be repairing them myself today.· I have a full understanding of the inner workings and each chip, having modified dozens of these computers in various ways for customers.· My original business involved building control interfaces for the User-Port.·
·· That being said I though you were trying to interface and control the 6526 directly.· It now appears you just need communication between the C=64 and the BASIC Stamp, which would involve connecting the BASIC Stamp I/O pins to the User Port.· This could be done but you may need to write some sort of communication code on the C=64 side to talk with the BASIC Stamp.· You can open a serial connection at several baud rates supported by the C=64.
·· Please clarify if I am correct about your connections.· As I said, my original thought was that you wanted to control the 6526 directly and the C=64 makes using this chip very easy by doing most of the work for you.· But for the BASIC Stamp it would be more difficult and you wouldn't be able to do it on one inside the C=64 directly.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
Perfect you know exactly the hardware I,m talking about. I,m not trying to interface directly with the 6526 chip, the commodore 64 will do this. I want to interface the stamp 2 to the c=64. I realize that I can use the rs232 for the communication between the 2, It,s no doubt the best way to go.
I,m more use to parallal communications, I was just checking to see if the I/O pins of the c=64 and the stamp 2 are parallal interfaceable.
I realize that there are other chip that I can use for this. Such as ie. from stamp 2 as output on pins say p0 to p3 for nibble to a CD4066 to give me an electronic switch to take place of the joysticks for input to game ports also a 74LS244 controlled by the stamp 2 should work.
I could come out of the c=64 with output on pb0 to pb3 and input to stamps 2's p4 to p7 either through another TTL chip for parallel input or go directly from c=64's pbo to pb3 into the stamps p4 to p7 pins for input if they can be interfaced directly.
I realize that I'm using alot of I/O pins on both the c=64 and the stamp but there are plenty for what I'm doing.
4 from c=64 to stamp for input and 4 from stamp to c=64 for output from stamp. It gives me the other 8 lines p8 to p15 on the stamp and the other 4 pins on the user port of the c=64 for a total of 12 and I also have the other game port on c=64 for another 5 inputs plus the one left over on the other game port = 6 more inputs. I realize that the c=64's keyboard and the game ports can't be used at the same time.
I'm also going to use the rpm program that parallax website shows using the melexis 90217 sensor to the stamp 2 and try to write a program so the c=64 can display the rpm's. The stamp 2 can monitor this and send the report to the c=64 when I ask.
If the stamp 2 is busy doing something else I could even have the c=64 monitor the rpm sensor directly through the c=64's cnt line.
Do I seem to be on the right track.
Also do you know if the stamp and the 64 can interface directly.
Thanks to you and also to kramer and gibbman for there input and I will check out the sites they suggested.
Regards
allie.
C=64 days were so fun back then... I ran a C64 based BBS system for many years. I purchased RAMLINK, put 16 megs of battery backed ram on it, a 9600 baud modem (and that was fast for the time)... all pre internet days for thoes not familuar with the time period... An interesting project to say the least... I've still my running C64, and a C128... 1541 & 81 drives, the old modem and a serial thermal printer to boot. What a time... Heck, I can still remember all the fun programs I wrote (try this one on... 3D graphic modeling... ) the games... SIDS... Oh yes... what a stroll down memory lane...
Heck, maybe I'll boot up the C64 and play some tonight... How I loved programming that computer...
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Just tossing my two bits worth into the bit bucket
KK
·
Ahhh, the good old days! This is a hoot! I did all of the above but with the Atari line - 400, 600, 800, ST! Factory trained Atari ST (68000) tech for a while. Did many a memory upgrade and external drive hacks! Yep, it sure WAS fun, however, I feel the same fun coming on as I work with the Parallax stuff - just LOTS smaller (well, the old-fart eyes perceive it that way anyway!!).
Thanks for the flashback!
Oh yea, the thread..... Hang in there allie, you'll get it!
I always liked playing with my commodore 64 and always wanted to interface to the user port but didn't have the book resourses until I found them on the internet books stores Amazon and Barns & Noble. The books that I found are: Commodore 64 interfacing blue book and Vic-20 interfacing blue book written by V.J. Georgiou, Ph.D. The other book that I found is Easy interfacing projects for the commodore 64 written by Jim Downey, Don Rindsberg, and William Isherwood. I also have the Commodore 64's programmer's reference guide along with the Forrest Mims Engineer's Notebook, as well as the radio shack's Engineer's Mini-Notebooks and lots of reference books on TTL and CMOS. I like the TTL chips and I have Lots of them mostly the 74LSxxx series. That is why I want to use TTL. For circuits that I,m working on time and speed as well as power consumption are not critial issues. I have a few CMOS devices 74Hxxx and 4000 chips.
I've been thinking about this design for a few years now as I was buying my Sherline Milling and Lath machines and wanted to interface them to my commodore 64. I chose the c=64 because with sherlines stepper motor controllers (Excellent design by sherline's owner Joe Martin and the electronics designer Brian Mumford). IT's a good chance that the used the Basic Stamp line.
Brian also designed an step and direction input which can be controlled by another host like the basic stamp or the c=64. He also included two more lines for Sense and Acknowledge (ACK). He said he put these in the design in-case some one out there wants to build there own interface,***perfect for my design***. As soon as I seen this the first thing that came to mind of course was the commodore 64' user interface. That was before I started reading about the parallax's stamp line. I was debateing which way to go. Then I figured where the c=64 could display alot of info. to the screen, I would go that way. It can do a lot of math as well as store alot of infomation that I would have to look up in books, a lot of calculations could be automatic. The sherline controllers do the moving of the steppers in a very easy way to program. If I want to move the lath table 5 thousands of an inch all I have to program in the sherline controller is a few simple commands and include .005 and it done. Very easy to use.
The more that I read on parallax's basic's stamps the more I was convienced that the stamp for sure is going into this design.
When planning my interface board from c=64 to the relay control board, I am making sure the stamp 2 can have total control over the relay board at any time that I want it to. The relay board is going to be opto-coupled to c=64 or stamp 2.
So where as, I'm designing with both the c=64 and the stamp 2 for relay control they might as well interface with each other. Instead of getting into LCD readouts I'm going to try and take advantage of the c=64's screen. Hopefully I can write a program so info from the stamp 2 can be displayed on the c=64 screen. The stamp 2 can interface with parallel LCD's so it should be able to interface info in parallell to c=64.
With more help from this forum I have a good chance of going this. Thanks to parallax for the stamps and access to this forum and thanks to Brian Mumford for allowing his design to be interfaceable and also thanks to commodore 64 computers for there userport.
Regards
allie
·· A few notes first...You would be using serial not RS-232.· It's important to note that the RS-232 specification relates to the voltages, not the protocol.· In your case you'll be using TTL level serial so RS-232 does not apply.· This is important because of the levels and their state (True as opposed to inverted).
·· As for the joystick port and keyboard, it has been a long time, but I do not recall that limitation.· The joystick ports not only connect to a VIA but as I recall they also connect to the 6581 SID chip which handles reading the paddles, unless I am mixing up the Amiga again (It has been too many years).
·· Back to the subject at hand...It seems like you are also talking about some parallel inputs, but you will have a little trouble sending data that way without a latch line or something to tell the C=64 what is valid data.· If you devote 4 bits (NIB) for data one way and 4 bits the other, how does each side know when the data is valid?· For example, suppose you send a 0000, but read it again before new data was made available.· You may think the next reading is 0000 when it was supposed to be 1111.·
·· A Parallel Printer Port uses a latch line to let the printer know the current byte is available on the 8 data pins.· I know you mentioned serial originally but perhaps we need to decide what is getting connected where before proceeding or at least exactly what data is being exchanged and how and through what pins.
I am a little confused on current details.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
http://forums.parallax.com/showthread.php?p=464494
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
It seems that the chip is:
1. 'static protected' but I am not sure that means much
2. Will sink 3.2ma
3. Will source at best 1.0ma
You may want to have external pull-up resistors inbetween the BasicStamp and the Commodore 64. The BasicStamps I/O is far more robust at 25ma sink/source.
You seem to be on the right track by wanting to protect the Commodore from too much load. From what I understand, in the early days nearly all the microcomputers used sink [noparse][[/noparse]rather than source] because they couldn't handle much load.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
Sorry for the detour....
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
I,m moving to the thread you mentioned above and will have answers to your questions there.
Kramer I will try to compute the values of the pullups and put then in my design but I may need values from the experts, I'm only a baby yet.
Moving to the sandbox thread mentioned above.
allie
·· This was your thread and as you're still on topic you don't need to move.· I was referring to general discussion of older computers and software.· We already had a thread for that.· But you can keep your questions here regarding your original post.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
It,s o.k. to stay on this thread if you want, I'm enjoying it, and love hearing about those topics all have posted. That's if I'm allowed to say this , I'm still newbe and not sure of some guidelines as such.
I'll try to answer your questions on next post.
I did read the documents again and I have concerns about how to correctly use a pullup. The Commodore' chip has a 2.4volt positive threshold and a +7volt absolute limit. Does just pulling up to 5 volts spell disaster?
I suppose one could buffer the two with a bi-directional driver of some sort rather than do discrete components for 8 lines.
It would be even easier if the directions were fixed [noparse][[/noparse]say 4 bits in and 4 bits out]. Even opto-isolators would work.
Pages 572-5 of THE ART OF ELECTRONICS have various solutions for mixing Logic families. Including jumps from 3.3v to 5.0v logic. From what I read, most CMOS to TTL is okay and most TTL to CMOS is okay, but there are sub-classes that don't work.
It looks like your is in the 74C/4000B class [noparse][[/noparse]due to the wimpy current output], but there are @5volt versions and @10volt versions. I assume the @5volt.
From what I am reading, TTL to CMOS requires A pullup to +5 or use HCT logic to interface.
And CMOS to TTL is OKAY [noparse][[/noparse]but with a limited fan out (you docs say only 2 TTL)].
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
There is a conflict if the keyboard and the joystick ports are used at the same time. The joystick lines come from port A and B of CIA#1. Pins 1 through 4 of game port 1 connect to PA0 through PA3, respectively. Similarly, pins 1 through 4 of game port 2 connects to PB0 through PB3. The joystick lines serve double duty in the c=64. They connect to the keyboard matrix and are used every 60th of a second to scan the keyboard. During one of my test using an 74ls244 to interface the game port with my sherline controller to test the ack. line on sherline controller to c=64, everything worked fine as long as I didn't try to use keyboard at same time. The keyboard wouldn't work right if certain keys pressed. I just have to make sure my programming returns me back from the check the joystick subroutine before I use the keyboard. If both not used at the same time there is no problem.
Your other question asked if game ports shared with the sid chip for paddle on c=64 verses amiga.
Answer is yes.
Your comment on serial signals at TTL levels being inverted not the same as rs232 I understand what your saying. Sorry if I mis-worded some thing above.
Another question you asked was, how will c=64 or BS2 know when parallel nib is sent or ready to be read. C=64 has 3 handshaking lines avaliable on user port.
1: PA2 = Can be either input or output.
2: Flag 2 = Input only
3: PC2 = Output only. It goes low for one cycle (1us) every time the user port is written or read.
Of course I'll have to use a few more i/o lines on the BS2 to interface to these lines. May be I can set up a counter routine in BS2 to keep track of input or output using count and pulse. Then store or retrive info from look up or look down. I'll have to check out what's available.
I'll Let you know what pins I'm going to use from BS2 to c=64 or may be I should call it ports. I'm going to try to calcuate what ohms of resistance that I should use from Bs2 to C=64 for pull ups. Or may be I'll use the 74ls244 to interface to game port from the BS2. What do you think on this.
Regards
allie
I have no problem using 4 lines for input only to c=64's game port and the other 4 lines for output from c=64 to Bs2. For what I'm doing there should be enough lines left.
Before I read this post I sent one to Chris asking this question about a 74ls244. What's your though's on the mentioned device.
Regards
allie
The use of a +5 volt system doesn't seem to be a problem as I/O are +7volts maxium.
Maybe a year ago, maybe longer I read the pages I mentioned above in detail. The main theme is that logic has improved in stability and durablity. The details mention several quirks. 74LS??? were introduced in 1976, 74HC??? and 74HCT??? in 1982.
The 74HC??? trigger at 1/2 supply voltage [noparse][[/noparse]seems to be a problem with the 2.4volt threshold] while the 74HCT??? trigger at 1.4 volts.
Nonetheless the 74LS triggers at 1.1 volts. All seem useful, but Pages 574-5 warns of possible dynamic incompatibiltiy when trying to drive edge-sensitive inputs from the 74C/4000B type to the 74HC??? [noparse][[/noparse]and the later 74AC???] as the transistions are too slow.
So, it seems the 74LS244 logic is a likely good fit. Seems to me that it won't hurt anything even if for some reason it doesn't work. But, if you start to fan out connections, be very careful.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)
······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
My first design before I decided to use the BS-2 was to come out of the c=64 into an ULN2803 then go into PS2502-4{Photo Darlington & Transistor / Detector) then go into an 74LS240.
Of course I have to put in the current limiting resistors between the ULN2803 and opto-coupler, as well as the pull up resistors between the opto-coupler and the 74LS240. Then I can parallel to my relay board.
Could I use this design to come from c=64 to BS-2. Would the BS-2 work well with inputs from the 74LS240.
I,d like to go this way as the other 4 outputs from c=64 will use this method and I have the parts.
regards
allie from the eastern coast of Canada : Nova Scotia
I don't have any programs to draw circuits other then the paint program in my accessories. If I draw a circuit with this do you know if I can input it to this forum thread.
regards
allie
·· It will be interesting to hear how this all goes.· If I were you I would have an extra C=64 handy for doing this on.· I remember my first transistor device interface...A little smoke and it was bye-bye user port.· Come to think of it that's how I got started repairing these things in the first place!
·· Load levels on the User Port were never much of a concern to me since I usually used Octal Buffers or transistors to drive external devices.· I had designed a nice circuit for using the cartridge port for 32 channel I/O but that information is lost forever in the bit bucket.· Unfortunately as I was telling a few people in the other thread I no longer have my old Tech Doc files, schematics and code for the C=64 since I had all of that on floppy disks and over time the Memorex Floppy Disks just seemed to wear out (lose data, oxidize, whatever) even though I never used them.· Heck they won't even format so.
·· In fact, recently I wanted to look back at a very clever keyscan routine I developed for the Z80 and when I went to read the disk, yep, you guessed it, read error on drive A:.· So I found one of my old EPROM chips and read the contents into the computer, used a Z80 disassembler and manually restored the data segments and labels.· Talk about work.· Not willing to put that effort into C=64/Amiga stuff anymore.
·· Here's a little tip for you all...ZIP Disks.· Unlike Floppy Disks these verify writing to the disk, have a longer shelf life, and can report failure of data before it's completely lost.· Never commit anything long-term to a CD-R as often they'll go corrupt within 1 to 2 years.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
Thanks for that advice. I will go with opto-coupling. I have another c=64. I bought it on e-bay but it's not working I am testing it, But it looks like new. It will be good learning for me to know the inwards of the 64 as I'm planning to keep using them as long as I can still get them. There seems to be a lot on e-bay as well as some companys still selling them.
Can the 74LS240 chip give input to the BS2.
regards
allie
·· As I recall the chips I used were the 72LS244 and the 74LS374.· Part of my cartridge interface used a bi-directional octal buffer 74LSxxx but I don't recall the part number.· These are simply what I used.· The 74xx244 chip is the non-inverting version of the 74xx240.· So bear in mind using the 74xx240 will inverter the state of the I/O lines.· opto-coupling is good for some circuits but I don't know if you need it here.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
I realize the 74xx240 will invert but that's what I want. As you know the c=64 I/O pins assume the high state on start-up, I want the other end of the interface to start with low's. I realize the opto-coupling may not be required here but the extra protection should not hurt anything. I have some 74LS245's which are octal bus transceivers.
allie
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com
Two weeks ago I gave away a full set of TechDocs and an SX-64...someone with an idea for using Commodores in FIRST robotics...small world. I do still have a "bug-tray-box" full of '64 and Amiga support chips, though. Wonder if they're worth anything?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Truly Understand the Fundamentals and the Path will be so much easier...