| Which latch to use? 74HC574 or 74HCT574 [message #351628] |
Tue, 29 August 2017 21:53  |
anthonypaulo
Messages: 531
Registered: September 2013
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I'm looking to have my Raspberry Pi communicate with the Apple IIe via a peripheral slot and have decided that the "bus" I'm going to use to interface them both is the 574. I have some 374's in front of me but I much prefer the pin arrangement on the 574. My question is, should I use the CMOS or TTL logic level version? Also, what level converter would you guys recommend for 3.3 -> 5 and vice-versa?
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| Which latch to use? 74HC574 or 74HCT574 [message #351655 is a reply to message #351628] |
Wed, 30 August 2017 10:26  |
anthonypaulo
Messages: 531
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Never mind which latch to use, mdj answered this nicely on march 8th in thread "what hardware is missing from the apple II"; his recommendation is to go with the TTL version.
That leaves my question on level translator open and I'd appreciate some advice from the experts.
Cheers!
Anthony
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #351656 is a reply to message #351628] |
Wed, 30 August 2017 10:31 |
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Originally posted by: cb meeks
On Tuesday, August 29, 2017 at 9:53:09 PM UTC-4, Anthony Ortiz wrote:
> I'm looking to have my Raspberry Pi communicate with the Apple IIe via a peripheral slot and have decided that the "bus" I'm going to use to interface them both is the 574. I have some 374's in front of me but I much prefer the pin arrangement on the 574. My question is, should I use the CMOS or TTL logic level version? Also, what level converter would you guys recommend for 3.3 -> 5 and vice-versa?
I don't know what conclusion you came to but I thought I'd mention some advice I got from the 6502 forums.
Some of those guys have been using 74LVC244A for voltage conversions. You can power it with 3V3 but the inputs are still 5V tolerant.
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #351657 is a reply to message #351628] |
Wed, 30 August 2017 10:33 |
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Originally posted by: cb meeks
On Tuesday, August 29, 2017 at 9:53:09 PM UTC-4, Anthony Ortiz wrote:
> I'm looking to have my Raspberry Pi communicate with the Apple IIe via a peripheral slot and have decided that the "bus" I'm going to use to interface them both is the 574. I have some 374's in front of me but I much prefer the pin arrangement on the 574. My question is, should I use the CMOS or TTL logic level version? Also, what level converter would you guys recommend for 3.3 -> 5 and vice-versa?
WAIT...you said LATCH.
Sorry...never mind. I didn't read that closely.
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #351665 is a reply to message #351658] |
Wed, 30 August 2017 13:38 |
anthonypaulo
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Okay, some more head scratching and google searching I discovered that the 74HCT series (the T for TTL is important here) will do the level transformation needed from 3.3v and register as the appropriate logic 0 or 1. This means the 74HC574 will work for uni-directional communication from the 3.3v Pi to the 5v Apple II bus. Now what I need is to go from 5v to 3.3v and I believe the 74HC4050 fits the bill, though I wish they would make them octal instead of hex.
Would someone please confirm or deny my findings?
Thanks!
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #351676 is a reply to message #351668] |
Wed, 30 August 2017 17:11 |
anthonypaulo
Messages: 531
Registered: September 2013
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Okay I think I got it now... SN74LVC245A octal bus transceiver with 3-state outputs lets me read from the 5v apple ii bus to the raspberry pi 3.3v GPIO and float it when not in use. Transceiver is overkill for my needs since I just need it one-way but I got tired of searching through a bajillion different parts.
I'll post an update once I get the parts and test them out. Can't wait!
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352076 is a reply to message #351676] |
Fri, 08 September 2017 14:41 |
anthonypaulo
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I received my SN74LVC245AN and was hooking it up for 3.3v -> 5v translation but As I read the data sheet I'm starting to think I made a mistake... although the specs state that it accepts input and supply voltages up to 6.5, the feature section states that it down-converts from 5 or 3.3 to 1.8, not vice versa. I'm guessing I read it wrong, that I can't feed an input at 3.3v and supply at 5v and expect it to work?
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352132 is a reply to message #352076] |
Sat, 09 September 2017 23:37 |
anthonypaulo
Messages: 531
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Okay, so I'm using an SN74LVC245A Octal Bus Transceiver to level-translate and buffer my Apple IIgs 1mhz (Phase 0) timer signal from 5v down to 3.3v and I am seeing some noise (or whatever it is) when reading the signal. Here is a pic of the source clock (top) and the level-translated 3.3v output of the same clock (bottom) : https://drive.google.com/file/d/0B-ZQ2AnS2r_6RlNrTW1tTDhvODh EZTdwUExXS2hDSEQ0aU1Z/view?usp=sharing
I see over/under shoot, don't know if that's normal, but the high-level of the 3.3v signal has less overshoot but more wavy than the low level; definitely not symmetrical! When polling the translated 3.3 clock signal on my Pi in a tight loop I get the data seen at the end of this post.
Any ideas?
[0 is LO, 1 is HI] followed by number of sequential occurrences
0 = 14076,1 = 34867,0 = 1,1 = 11,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 6,1 = 2,0 = 6,1 = 2,0 = 2,1 = 3,0 = 5,1 = 2,0 = 2,1 = 2,0 = 2,1 = 1,0 = 1,1 = 1,0 = 5,1 = 1,0 = 9,1 = 1,0 = 31670,1 = 34797,0 = 1,1 = 11,0 = 1,1 = 42,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 = 3,1 = 1,0 = 7,1 = 1,0 = 3,1 = 2,0 = 29631,1 = 34870,0 = 1,1 = 11,0 = 1,1 = 11,0 = 2,1 = 2,0 = 2,1 = 29,0 = 1,1 = 3,0 = 1,1 = 7,0 = 1,1 = 3,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31725,1 = 34871,0 = 1,1 = 3,0 = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 11,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 2,0 = 31674,1 = 32819,0 = 1,1 = 55,0 = 1,1 = 2,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 3,1 = 1,0 = 3,1 = 2,0 = 5,1 = 1,0 = 31686,1 = 34733,0 = 1,1 = 49,0 = 1,1 = 8,0 = 1,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 = 1,0 = 8,1 = 1,0 = 31688,1 = 34876,0 = 1,1 = 1,0 = 1,1 = 9,0 = 1,1 = 3,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 1,1 = 4,0 = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 = 4,0 = 1,1 = 2,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31692,1 = 32839,0 = 1,1 = 52,0 = 3,1 = 2,0 = 7,1 = 1,0 = 31691,1 = 34818,0 = 1,1 = 11,0 = 1,1 = 42,0 = 3,1 = 1,0 = 8,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 31720,1 = 32839,0 = 1,1 = 40,0 = 1,1 = 2,0 = 2,1 = 1,0 = 3,1 = 2,0 = 31699,1 = 34860,0 = 1,1 = 18,0 = 1,1 = 7,0 = 2,1 = 2,0 = 2,1 = 2,0 = 2,1 = 2,0 = 4,1 = 3,0 = 3,1 = 2,0 = 3,1 = 1,0 = 1,1 = 2,0 = 20,1 = 1,0 = 1,1 = 1,0 = 31670,1 = 34767,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 5,0 = 2,1 = 2,0 = 7,1 = 2,0 = 1,1 = 2,0 = 1,1 = 3,0 = 2,1 = 3,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 1,0 = 3,1 = 1,0 = 4,1 = 1,0 = 31673,1 = 32906,0 = 1,1 = 6,0 = 2,1 = 6,0 = 2,1 = 2,0 = 33,1 = 1,0 = 31608,1 = 34914,0 = 1,1 = 12,0 = 1,1 = 6,0 = 2,1 = 2,0 = 6,1 = 1,0 = 26,1 = 1,0 = 17,1 = 1,0 = 31721,1 = 32810,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 5,0 = 3,1 = 1,0 = 7,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 = 1,0 = 2,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 6,0 = 31696,1 = 34814,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 3,0 = 2,1 = 5,0 = 3,1 = 1,0 = 3,1 = 2,0 = 1,1 = 6,0 = 2,1 = 2,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 = 3,1 = 1,0 = 2,1 = 1,0 = 31632,1 = 34870,0 = 1,1 = 3,0 = 1,1 = 51,0 = 2,1 = 1,0 = 3,1 = 1,0 = 2,1 = 3,0 = 1,1 = 1,0 = 29726,1 = 34810,0 = 3,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 2,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 3,1 = 1,0 = 3,1 = 2,0 = 11,1 = 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 9,1 = 1,0 = 3,1 = 1,0 = 1,1 = 1,0 = 31615,1 = 34848,0 = 1,1 = 27,0 = 1,1 = 7,0 = 2,1 = 5,0 = 1,1 = 3,0 = 3,1 = 6,0 = 1,1 = 2,0 = 2,1 = 2,0 = 31747,1 = 32873,0 = 1,1 = 7,0 = 1,1 = 3,0 = 2,1 = 1,0 = 3,1 = 2,0 = 21,1 = 1
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352137 is a reply to message #352132] |
Sun, 10 September 2017 05:41 |
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Originally posted by: Jorge
On Sunday, September 10, 2017 at 5:37:40 AM UTC+2, Anthony Ortiz wrote:
> When polling the translated 3.3 clock signal on my Pi in a tight loop I get the data seen at the end of this post.
>
> Any ideas?
The signal is about right imo, that ringing is not too bad, find a better/closer/shorter path to GND in which to plug the scope's GND tip to be sure. IOW the signals only look perfectly square in the datasheets... :-)
WRT the big number(s) of sequential ocurrences (e.g. 0 = 31699,1 = 34860) that is also normal because the Pi is time slicing your polling routine. Also, at what frequency are you sampling the gpios? See this:
http://codeandlife.com/2012/07/03/benchmarking-raspberry-pi- gpio-speed/
To poll the gpio C is best. But even so it will be time sliced out every so often by the scheduler.
--
Jorge
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352170 is a reply to message #352137] |
Sun, 10 September 2017 18:21 |
anthonypaulo
Messages: 531
Registered: September 2013
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On Sunday, September 10, 2017 at 5:41:47 AM UTC-4, Jorge wrote:
> On Sunday, September 10, 2017 at 5:37:40 AM UTC+2, Anthony Ortiz wrote:
>> When polling the translated 3.3 clock signal on my Pi in a tight loop I get the data seen at the end of this post.
>>
>> Any ideas?
>
> The signal is about right imo, that ringing is not too bad, find a better/closer/shorter path to GND in which to plug the scope's GND tip to be sure.. IOW the signals only look perfectly square in the datasheets... :-)
>
> WRT the big number(s) of sequential ocurrences (e.g. 0 = 31699,1 = 34860) that is also normal because the Pi is time slicing your polling routine. Also, at what frequency are you sampling the gpios? See this:
>
> http://codeandlife.com/2012/07/03/benchmarking-raspberry-pi- gpio-speed/
>
> To poll the gpio C is best. But even so it will be time sliced out every so often by the scheduler.
>
> --
> Jorge
Pi 3 runs at 1.1ghz and i'm sampling in a tight loop. The big number of sequential occurrences are strange because 1) they are supposed to be about the same but there is a 10% difference and 2) what's with all the other random noise? it seems to only happen right after the 1-> 0 transition but never after the 0 -> 1 transition... for some reason 0 -> 1 is perfectly clean! Also, I don't know why I'm getting so many samples... the Pi 3 is 1.1ghz, which is only 1100 times the speed of the 1mhz clock, which means I should get at most 1100 samples, not 60k+! Strange...
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352173 is a reply to message #352171] |
Sun, 10 September 2017 18:47 |
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Originally posted by: Jorge
On Monday, September 11, 2017 at 12:25:34 AM UTC+2, Anthony Ortiz wrote:
> I'm doing this bare metal.
Wow that's cool! Have you got it @github perhaps? Can I see it or is it private? Now I'm curious, what exactly are you trying to do, if I may ask?
Then I've got another, new theory: what you're seeing may be a pattern of interference, a sort of "moiré".
Another idea: the rpi is prone to overheating when run @full speed, perhaps it's overheating? But that should not be it because you are using just one core, are you?
I've got no more ideas, it's too late for that. Good night!
Cheers,
--
Jorge.
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352256 is a reply to message #352132] |
Sun, 10 September 2017 19:20 |
Michael J. Mahon
Messages: 1767
Registered: October 2012
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Anthony Ortiz <anthonypaulo@gmail.com> wrote:
> Okay, so I'm using an SN74LVC245A Octal Bus Transceiver to
> level-translate and buffer my Apple IIgs 1mhz (Phase 0) timer signal from
> 5v down to 3.3v and I am seeing some noise (or whatever it is) when
> reading the signal. Here is a pic of the source clock (top) and the
> level-translated 3.3v output of the same clock (bottom) :
> https://drive.google.com/file/d/0B-ZQ2AnS2r_6RlNrTW1tTDhvODh EZTdwUExXS2hDSEQ0aU1Z/view?usp=sharing
>
> I see over/under shoot, don't know if that's normal, but the high-level
> of the 3.3v signal has less overshoot but more wavy than the low level;
> definitely not symmetrical! When polling the translated 3.3 clock signal
> on my Pi in a tight loop I get the data seen at the end of this post.
>
> Any ideas?
>
> [0 is LO, 1 is HI] followed by number of sequential occurrences
>
> 0 = 14076,1 = 34867,0 = 1,1 = 11,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
> 1,1 = 2,0 = 2,1 = 2,0 = 6,1 = 2,0 = 6,1 = 2,0 = 2,1 = 3,0 = 5,1 = 2,0 =
> 2,1 = 2,0 = 2,1 = 1,0 = 1,1 = 1,0 = 5,1 = 1,0 = 9,1 = 1,0 = 31670,1 =
> 34797,0 = 1,1 = 11,0 = 1,1 = 42,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
> 1,1 = 2,0 = 3,1 = 1,0 = 7,1 = 1,0 = 3,1 = 2,0 = 29631,1 = 34870,0 = 1,1 =
> 11,0 = 1,1 = 11,0 = 2,1 = 2,0 = 2,1 = 29,0 = 1,1 = 3,0 = 1,1 = 7,0 = 1,1
> = 3,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31725,1 = 34871,0 = 1,1 = 3,0
> = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 1,0 = 1,1 = 1,0 =
> 1,1 = 11,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 3,0 = 1,1 = 1,0 =
> 3,1 = 2,0 = 31674,1 = 32819,0 = 1,1 = 55,0 = 1,1 = 2,0 = 1,1 = 3,0 = 3,1
> = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 3,1 =
> 1,0 = 3,1 = 2,0 = 5,1 = 1,0 = 31686,1 = 34733,0 = 1,1 = 49,0 = 1,1 = 8,0
> = 1,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 = 1,0 = 8,1 = 1,0 = 31688,1 =
> 34876,0 = 1,1 = 1,0 = 1,1 = 9,0 = 1,1 = 3,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1
> = 2,0 = 2,1 = 2,0 = 1,1 = 4,0 = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 =
> 4,0 = 1,1 = 2,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 =
> 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31692,1 = 32839,0 = 1,1 = 52,0 = 3,1 = 2,0
> = 7,1 = 1,0 = 31691,1 = 34818,0 = 1,1 = 11,0 = 1,1 = 42,0 = 3,1 = 1,0 =
> 8,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 31720,1 = 32839,0 = 1,1 =
> 40,0 = 1,1 = 2,0 = 2,1 = 1,0 = 3,1 = 2,0 = 31699,1 = 34860,0 = 1,1 = 18,0
> = 1,1 = 7,0 = 2,1 = 2,0 = 2,1 = 2,0 = 2,1 = 2,0 = 4,1 = 3,0 = 3,1 = 2,0 =
> 3,1 = 1,0 = 1,1 = 2,0 = 20,1 = 1,0 = 1,1 = 1,0 = 31670,1 = 34767,0 = 1,1
> = 3,0 = 1,1 = 2,0 = 2,1 = 5,0 = 2,1 = 2,0 = 7,1 = 2,0 = 1,1 = 2,0 = 1,1 =
> 3,0 = 2,1 = 3,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 1,0 = 3,1 =
> 1,0 = 4,1 = 1,0 = 31673,1 = 32906,0 = 1,1 = 6,0 = 2,1 = 6,0 = 2,1 = 2,0 =
> 33,1 = 1,0 = 31608,1 = 34914,0 = 1,1 = 12,0 = 1,1 = 6,0 = 2,1 = 2,0 = 6,1
> = 1,0 = 26,1 = 1,0 = 17,1 = 1,0 = 31721,1 = 32810,0 = 2,1 = 3,0 = 1,1 =
> 1,0 = 3,1 = 5,0 = 3,1 = 1,0 = 7,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 =
> 1,0 = 2,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 6,0 = 31696,1
> = 34814,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 3,0 = 2,1 = 5,0 = 3,1 = 1,0 =
> 3,1 = 2,0 = 1,1 = 6,0 = 2,1 = 2,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 =
> 3,1 = 1,0 = 2,1 = 1,0 = 31632,1 = 34870,0 = 1,1 = 3,0 = 1,1 = 51,0 = 2,1
> = 1,0 = 3,1 = 1,0 = 2,1 = 3,0 = 1,1 = 1,0 = 29726,1 = 34810,0 = 3,1 = 1,0
> = 1,1 = 1,0 = 1,1 = 1,0 = 2,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 3,1 = 1,0 =
> 3,1 = 2,0 = 11,1 = 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 9,1 = 1,0 = 3,1 = 1,0 =
> 1,1 = 1,0 = 31615,1 = 34848,0 = 1,1 = 27,0 = 1,1 = 7,0 = 2,1 = 5,0 = 1,1
> = 3,0 = 3,1 = 6,0 = 1,1 = 2,0 = 2,1 = 2,0 = 31747,1 = 32873,0 = 1,1 = 7,0
> = 1,1 = 3,0 = 2,1 = 1,0 = 3,1 = 2,0 = 21,1 = 1
>
Looks like a lot of ringing.
Are you using a 10x probe? A 1x probe will produce this effect. Using a
10x probe greatly reduces the load on the circuit and also reduces the
effect of the probe and its cable.
This ringing is almost certainly the result of the probe and not the
circuit.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352257 is a reply to message #352256] |
Sun, 10 September 2017 20:39 |
anthonypaulo
Messages: 531
Registered: September 2013
Karma: 0
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Senior Member |
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On Sunday, September 10, 2017 at 7:20:27 PM UTC-4, Michael J. Mahon wrote:
>> Okay, so I'm using an SN74LVC245A Octal Bus Transceiver to
>> level-translate and buffer my Apple IIgs 1mhz (Phase 0) timer signal from
>> 5v down to 3.3v and I am seeing some noise (or whatever it is) when
>> reading the signal. Here is a pic of the source clock (top) and the
>> level-translated 3.3v output of the same clock (bottom) :
>> https://drive.google.com/file/d/0B-ZQ2AnS2r_6RlNrTW1tTDhvODh EZTdwUExXS2hDSEQ0aU1Z/view?usp=sharing
>>
>> I see over/under shoot, don't know if that's normal, but the high-level
>> of the 3.3v signal has less overshoot but more wavy than the low level;
>> definitely not symmetrical! When polling the translated 3.3 clock signal
>> on my Pi in a tight loop I get the data seen at the end of this post.
>>
>> Any ideas?
>>
>> [0 is LO, 1 is HI] followed by number of sequential occurrences
>>
>> 0 = 14076,1 = 34867,0 = 1,1 = 11,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
>> 1,1 = 2,0 = 2,1 = 2,0 = 6,1 = 2,0 = 6,1 = 2,0 = 2,1 = 3,0 = 5,1 = 2,0 =
>> 2,1 = 2,0 = 2,1 = 1,0 = 1,1 = 1,0 = 5,1 = 1,0 = 9,1 = 1,0 = 31670,1 =
>> 34797,0 = 1,1 = 11,0 = 1,1 = 42,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
>> 1,1 = 2,0 = 3,1 = 1,0 = 7,1 = 1,0 = 3,1 = 2,0 = 29631,1 = 34870,0 = 1,1 =
>> 11,0 = 1,1 = 11,0 = 2,1 = 2,0 = 2,1 = 29,0 = 1,1 = 3,0 = 1,1 = 7,0 = 1,1
>> = 3,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31725,1 = 34871,0 = 1,1 = 3,0
>> = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 1,0 = 1,1 = 1,0 =
>> 1,1 = 11,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 3,0 = 1,1 = 1,0 =
>> 3,1 = 2,0 = 31674,1 = 32819,0 = 1,1 = 55,0 = 1,1 = 2,0 = 1,1 = 3,0 = 3,1
>> = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 3,1 =
>> 1,0 = 3,1 = 2,0 = 5,1 = 1,0 = 31686,1 = 34733,0 = 1,1 = 49,0 = 1,1 = 8,0
>> = 1,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 = 1,0 = 8,1 = 1,0 = 31688,1 =
>> 34876,0 = 1,1 = 1,0 = 1,1 = 9,0 = 1,1 = 3,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1
>> = 2,0 = 2,1 = 2,0 = 1,1 = 4,0 = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 =
>> 4,0 = 1,1 = 2,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 =
>> 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31692,1 = 32839,0 = 1,1 = 52,0 = 3,1 = 2,0
>> = 7,1 = 1,0 = 31691,1 = 34818,0 = 1,1 = 11,0 = 1,1 = 42,0 = 3,1 = 1,0 =
>> 8,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 31720,1 = 32839,0 = 1,1 =
>> 40,0 = 1,1 = 2,0 = 2,1 = 1,0 = 3,1 = 2,0 = 31699,1 = 34860,0 = 1,1 = 18,0
>> = 1,1 = 7,0 = 2,1 = 2,0 = 2,1 = 2,0 = 2,1 = 2,0 = 4,1 = 3,0 = 3,1 = 2,0 =
>> 3,1 = 1,0 = 1,1 = 2,0 = 20,1 = 1,0 = 1,1 = 1,0 = 31670,1 = 34767,0 = 1,1
>> = 3,0 = 1,1 = 2,0 = 2,1 = 5,0 = 2,1 = 2,0 = 7,1 = 2,0 = 1,1 = 2,0 = 1,1 =
>> 3,0 = 2,1 = 3,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 1,0 = 3,1 =
>> 1,0 = 4,1 = 1,0 = 31673,1 = 32906,0 = 1,1 = 6,0 = 2,1 = 6,0 = 2,1 = 2,0 =
>> 33,1 = 1,0 = 31608,1 = 34914,0 = 1,1 = 12,0 = 1,1 = 6,0 = 2,1 = 2,0 = 6,1
>> = 1,0 = 26,1 = 1,0 = 17,1 = 1,0 = 31721,1 = 32810,0 = 2,1 = 3,0 = 1,1 =
>> 1,0 = 3,1 = 5,0 = 3,1 = 1,0 = 7,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 =
>> 1,0 = 2,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 6,0 = 31696,1
>> = 34814,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 3,0 = 2,1 = 5,0 = 3,1 = 1,0 =
>> 3,1 = 2,0 = 1,1 = 6,0 = 2,1 = 2,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 =
>> 3,1 = 1,0 = 2,1 = 1,0 = 31632,1 = 34870,0 = 1,1 = 3,0 = 1,1 = 51,0 = 2,1
>> = 1,0 = 3,1 = 1,0 = 2,1 = 3,0 = 1,1 = 1,0 = 29726,1 = 34810,0 = 3,1 = 1,0
>> = 1,1 = 1,0 = 1,1 = 1,0 = 2,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 3,1 = 1,0 =
>> 3,1 = 2,0 = 11,1 = 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 9,1 = 1,0 = 3,1 = 1,0 =
>> 1,1 = 1,0 = 31615,1 = 34848,0 = 1,1 = 27,0 = 1,1 = 7,0 = 2,1 = 5,0 = 1,1
>> = 3,0 = 3,1 = 6,0 = 1,1 = 2,0 = 2,1 = 2,0 = 31747,1 = 32873,0 = 1,1 = 7,0
>> = 1,1 = 3,0 = 2,1 = 1,0 = 3,1 = 2,0 = 21,1 = 1
>>
>
> Looks like a lot of ringing.
>
> Are you using a 10x probe? A 1x probe will produce this effect. Using a
> 10x probe greatly reduces the load on the circuit and also reduces the
> effect of the probe and its cable.
>
> This ringing is almost certainly the result of the probe and not the
> circuit.
>
> --
> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Wow! I just checked the probes and indeed they are set to 1x. I'll set them to 10x and see what happens. I'm just using an oscilloscope for the first time so I'm very new to this and only know the really basic stuff. Will post my results soon!
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352259 is a reply to message #352257] |
Sun, 10 September 2017 21:23 |
anthonypaulo
Messages: 531
Registered: September 2013
Karma: 0
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Senior Member |
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On Sunday, September 10, 2017 at 8:39:45 PM UTC-4, Anthony Ortiz wrote:
> On Sunday, September 10, 2017 at 7:20:27 PM UTC-4, Michael J. Mahon wrote:
>>> Okay, so I'm using an SN74LVC245A Octal Bus Transceiver to
>>> level-translate and buffer my Apple IIgs 1mhz (Phase 0) timer signal from
>>> 5v down to 3.3v and I am seeing some noise (or whatever it is) when
>>> reading the signal. Here is a pic of the source clock (top) and the
>>> level-translated 3.3v output of the same clock (bottom) :
>>> https://drive.google.com/file/d/0B-ZQ2AnS2r_6RlNrTW1tTDhvODh EZTdwUExXS2hDSEQ0aU1Z/view?usp=sharing
>>>
>>> I see over/under shoot, don't know if that's normal, but the high-level
>>> of the 3.3v signal has less overshoot but more wavy than the low level;
>>> definitely not symmetrical! When polling the translated 3.3 clock signal
>>> on my Pi in a tight loop I get the data seen at the end of this post.
>>>
>>> Any ideas?
>>>
>>> [0 is LO, 1 is HI] followed by number of sequential occurrences
>>>
>>> 0 = 14076,1 = 34867,0 = 1,1 = 11,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
>>> 1,1 = 2,0 = 2,1 = 2,0 = 6,1 = 2,0 = 6,1 = 2,0 = 2,1 = 3,0 = 5,1 = 2,0 =
>>> 2,1 = 2,0 = 2,1 = 1,0 = 1,1 = 1,0 = 5,1 = 1,0 = 9,1 = 1,0 = 31670,1 =
>>> 34797,0 = 1,1 = 11,0 = 1,1 = 42,0 = 1,1 = 3,0 = 3,1 = 2,0 = 1,1 = 3,0 =
>>> 1,1 = 2,0 = 3,1 = 1,0 = 7,1 = 1,0 = 3,1 = 2,0 = 29631,1 = 34870,0 = 1,1 =
>>> 11,0 = 1,1 = 11,0 = 2,1 = 2,0 = 2,1 = 29,0 = 1,1 = 3,0 = 1,1 = 7,0 = 1,1
>>> = 3,0 = 2,1 = 3,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31725,1 = 34871,0 = 1,1 = 3,0
>>> = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 1,0 = 1,1 = 1,0 =
>>> 1,1 = 11,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 3,0 = 1,1 = 1,0 =
>>> 3,1 = 2,0 = 31674,1 = 32819,0 = 1,1 = 55,0 = 1,1 = 2,0 = 1,1 = 3,0 = 3,1
>>> = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 3,1 =
>>> 1,0 = 3,1 = 2,0 = 5,1 = 1,0 = 31686,1 = 34733,0 = 1,1 = 49,0 = 1,1 = 8,0
>>> = 1,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 = 1,0 = 8,1 = 1,0 = 31688,1 =
>>> 34876,0 = 1,1 = 1,0 = 1,1 = 9,0 = 1,1 = 3,0 = 1,1 = 4,0 = 1,1 = 3,0 = 1,1
>>> = 2,0 = 2,1 = 2,0 = 1,1 = 4,0 = 1,1 = 7,0 = 1,1 = 3,0 = 1,1 = 2,0 = 1,1 =
>>> 4,0 = 1,1 = 2,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 = 2,0 = 1,1 = 1,0 = 1,1 =
>>> 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 31692,1 = 32839,0 = 1,1 = 52,0 = 3,1 = 2,0
>>> = 7,1 = 1,0 = 31691,1 = 34818,0 = 1,1 = 11,0 = 1,1 = 42,0 = 3,1 = 1,0 =
>>> 8,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 1,1 = 1,0 = 31720,1 = 32839,0 = 1,1 =
>>> 40,0 = 1,1 = 2,0 = 2,1 = 1,0 = 3,1 = 2,0 = 31699,1 = 34860,0 = 1,1 = 18,0
>>> = 1,1 = 7,0 = 2,1 = 2,0 = 2,1 = 2,0 = 2,1 = 2,0 = 4,1 = 3,0 = 3,1 = 2,0 =
>>> 3,1 = 1,0 = 1,1 = 2,0 = 20,1 = 1,0 = 1,1 = 1,0 = 31670,1 = 34767,0 = 1,1
>>> = 3,0 = 1,1 = 2,0 = 2,1 = 5,0 = 2,1 = 2,0 = 7,1 = 2,0 = 1,1 = 2,0 = 1,1 =
>>> 3,0 = 2,1 = 3,0 = 1,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 1,0 = 3,1 =
>>> 1,0 = 4,1 = 1,0 = 31673,1 = 32906,0 = 1,1 = 6,0 = 2,1 = 6,0 = 2,1 = 2,0 =
>>> 33,1 = 1,0 = 31608,1 = 34914,0 = 1,1 = 12,0 = 1,1 = 6,0 = 2,1 = 2,0 = 6,1
>>> = 1,0 = 26,1 = 1,0 = 17,1 = 1,0 = 31721,1 = 32810,0 = 2,1 = 3,0 = 1,1 =
>>> 1,0 = 3,1 = 5,0 = 3,1 = 1,0 = 7,1 = 2,0 = 1,1 = 1,0 = 3,1 = 2,0 = 3,1 =
>>> 1,0 = 2,1 = 1,0 = 1,1 = 1,0 = 1,1 = 2,0 = 2,1 = 2,0 = 2,1 = 6,0 = 31696,1
>>> = 34814,0 = 1,1 = 2,0 = 1,1 = 3,0 = 1,1 = 3,0 = 2,1 = 5,0 = 3,1 = 1,0 =
>>> 3,1 = 2,0 = 1,1 = 6,0 = 2,1 = 2,0 = 3,1 = 2,0 = 1,1 = 3,0 = 1,1 = 2,0 =
>>> 3,1 = 1,0 = 2,1 = 1,0 = 31632,1 = 34870,0 = 1,1 = 3,0 = 1,1 = 51,0 = 2,1
>>> = 1,0 = 3,1 = 1,0 = 2,1 = 3,0 = 1,1 = 1,0 = 29726,1 = 34810,0 = 3,1 = 1,0
>>> = 1,1 = 1,0 = 1,1 = 1,0 = 2,1 = 3,0 = 1,1 = 2,0 = 2,1 = 2,0 = 3,1 = 1,0 =
>>> 3,1 = 2,0 = 11,1 = 1,0 = 1,1 = 1,0 = 3,1 = 1,0 = 9,1 = 1,0 = 3,1 = 1,0 =
>>> 1,1 = 1,0 = 31615,1 = 34848,0 = 1,1 = 27,0 = 1,1 = 7,0 = 2,1 = 5,0 = 1,1
>>> = 3,0 = 3,1 = 6,0 = 1,1 = 2,0 = 2,1 = 2,0 = 31747,1 = 32873,0 = 1,1 = 7,0
>>> = 1,1 = 3,0 = 2,1 = 1,0 = 3,1 = 2,0 = 21,1 = 1
>>>
>>
>> Looks like a lot of ringing.
>>
>> Are you using a 10x probe? A 1x probe will produce this effect. Using a
>> 10x probe greatly reduces the load on the circuit and also reduces the
>> effect of the probe and its cable.
>>
>> This ringing is almost certainly the result of the probe and not the
>> circuit.
>>
>> --
>> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
>
> Wow! I just checked the probes and indeed they are set to 1x. I'll set them to 10x and see what happens. I'm just using an oscilloscope for the first time so I'm very new to this and only know the really basic stuff. Will post my results soon!
I tried setting probes to 10x but it squashed the original 5v clock signal and flatlined into a faint blinking horizontal line on the 3.3v level-translated clock signal.
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352276 is a reply to message #352259] |
Mon, 11 September 2017 11:20 |
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Originally posted by: Jorge
On Monday, September 11, 2017 at 3:23:22 AM UTC+2, Anthony Ortiz wrote:
>
> I tried setting probes to 10x but it squashed the original 5v clock signal and flatlined into a faint blinking horizontal line on the 3.3v level-translated clock signal.
That was to be expected. You've got to poke 10x in the scope settings for that probe/channel.
--
Jorge
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #352278 is a reply to message #352276] |
Mon, 11 September 2017 12:59 |
Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
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Senior Member |
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Jorge <jorge@jorgechamorro.com> wrote:
> On Monday, September 11, 2017 at 3:23:22 AM UTC+2, Anthony Ortiz wrote:
>>
>> I tried setting probes to 10x but it squashed the original 5v clock
>> signal and flatlined into a faint blinking horizontal line on the 3.3v
>> level-translated clock signal.
>
> That was to be expected. You've got to poke 10x in the scope settings for
> that probe/channel.
>
Right!
The 10x probe reduces resistive and capacitive loading by a factor of ten,
and it does that by attenuating the signal by a factor of ten.
That should not be a problem with logic-level signals, since the
oscilloscope has plenty of vertical gain to spare.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #353504 is a reply to message #353503] |
Tue, 26 September 2017 22:50 |
anthonypaulo
Messages: 531
Registered: September 2013
Karma: 0
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Senior Member |
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On Tuesday, September 26, 2017 at 10:47:08 PM UTC-4, Anthony Ortiz wrote:
> My transceiver datasheet is recommending a bypass capacitor for its 5v Vcc, which I'm sourcing from the 5v line on the Apple II bus. Any recommendations on parallel resistor/capacitor combo?
Sorry, forgot the other supply (it's dual supply)... one side sources 5v from Apple II, the other side sources 3.3v from Pi. I need bypass capacitors for both sides and could use some recommendations.
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #353521 is a reply to message #353504] |
Wed, 27 September 2017 02:12 |
Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
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Senior Member |
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Anthony Ortiz <anthonypaulo@gmail.com> wrote:
> On Tuesday, September 26, 2017 at 10:47:08 PM UTC-4, Anthony Ortiz wrote:
>> My transceiver datasheet is recommending a bypass capacitor for its 5v
>> Vcc, which I'm sourcing from the 5v line on the Apple II bus. Any
>> recommendations on parallel resistor/capacitor combo?
>
> Sorry, forgot the other supply (it's dual supply)... one side sources 5v
> from Apple II, the other side sources 3.3v from Pi. I need bypass
> capacitors for both sides and could use some recommendations.
>
Standard bypassing for drivers is 0.1uF from each supply to ground, as
close to the chip's power pins as possible.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #353528 is a reply to message #353521] |
Wed, 27 September 2017 06:11 |
anthonypaulo
Messages: 531
Registered: September 2013
Karma: 0
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Senior Member |
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Thanks Michael. Couple of related questions :
1) online I see mention of a parallel resistor; any particular one I should be using?
2) any particular type of capacitor (e.g. Ceramic?)
3) if I need to drive several transceivers, do I need a bypass capacitor for each one or can I drive them from a single one?
Thanks!
Anthony
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #353549 is a reply to message #353528] |
Wed, 27 September 2017 15:25 |
Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
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Senior Member |
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Anthony Ortiz <anthonypaulo@gmail.com> wrote:
> Thanks Michael. Couple of related questions :
>
> 1) online I see mention of a parallel resistor; any particular one I should be using?
In parallel with what? Is this a bus terminator (one resistor per output)?
That would be unnecessary for a short bus.
> 2) any particular type of capacitor (e.g. Ceramic?)
Yes, typically ceramic/monolithic. All printed circuit boards are covered
with them!
> 3) if I need to drive several transceivers, do I need a bypass capacitor
> for each one or can I drive them from a single one?
Each chip should have a bypass cap.
> Thanks!
Glad to help--sounds like fun!
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
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| Re: Which latch to use? 74HC574 or 74HCT574 [message #353946 is a reply to message #353549] |
Sat, 07 October 2017 00:56 |
anthonypaulo
Messages: 531
Registered: September 2013
Karma: 0
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Senior Member |
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Thanks to everyone for all the assistance. Tonight I finally managed to interface my Pi with the Apple II bus at 1mhz and via GPIO read the three bytes from ROM at $FDED. Next is some writes, but tonight I sleep the sleep of babes...
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