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Author Topic: 6Mhz and more... (Read 25074 times)

Online pear

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Re: 6Mhz and more...
« Reply #60 on: 2017.July.12. 07:25:03 »
Nice chip but as new is available only version DS1077LZ-40+ (4,87-66,6 kHz MHz).
In addition, the microcontroller will anyway.
The DS1077 costs as much as the entire microcontroller.
I will try to do all programmatically.
The PIC18F14K22 has an internal clock of 64MHz (the processor cycle is 4 tacts). Maybe it is enough...
Always can look for another microcontroller.
« Last Edit: 2017.July.12. 09:16:30 by pear »

Online gflorez

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Re: 6Mhz and more...
« Reply #61 on: 2017.July.12. 09:03:49 »
Sorry, the top frequency of the DS1077LZ is in Mhz, not Khz, but I understand you want to do it simpler.

And comunicating the DS1077LZ with the microcontroller is a lot more work.

Online pear

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Re: 6Mhz and more...
« Reply #62 on: 2017.July.12. 09:14:50 »
You're right. It's MHz, an error is on TME site.

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Re: 6Mhz and more...
« Reply #63 on: 2017.July.12. 10:04:58 »
Now let's see what specs are needed:

For the Z80 we need the frequency to be double than nominal, i. e. for a 4Mhz stock processor we need 8Mhz from the oscillator, for a 6Mhz we need 12Mhz, and so on. Actually the top frequency of a turbo machine is 10Mhz, but may be Zozo could find some way to increase it, so I think we can't stop on the 20Mhz needed. (I already have 20Mhz Z80's installed on my two Enterprises, waiting for a hack...) .

Then, for the Exdos card is easier, because we don't need double frequencies, only the given 8,9.6,10,13.33333,16MHz

Also it could be funny to be capable of under-clock the processor....

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Re: 6Mhz and more...
« Reply #64 on: 2017.July.12. 10:21:41 »
Also it could be funny to be capable of under-clock the processor....
Once I tried it. Will be good for some games, for example Tombs of doom :ds_icon_cheesygrin:

Online pear

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Re: 6Mhz and more...
« Reply #65 on: 2017.July.12. 10:31:37 »
Well. I read some documentations.
The DS1077 has only a divider (range 2..1025). With a basic frequency of 40MHz you will get only 3 values of the set you are interested in (8,10 and 13.33 MHz).
My idea already I verified because the divisor only is not enough to get all the values.
I stayed with PIC (I already ordered). With a set frequency of 64MHz, I am able to generate a signal with a fundamental frequency of 16 MHz (and divided by subsequent integers). This gives us only two values from the set (16 and 8 MHz).
Therefore, you will need an additional multiplier.
I found a programmable PLL circuit ICS501 that can multiply the frequency.
This combination gives you all the value we have (and many others).

Base frequency Fb=16 MHz

16,00 MHz = Fb * 1/1
13,33 MHz = Fb * 5/6
10,00 Mhz = Fb * 5/8
 9,60 MHz = Fb * 6/10
 8,00 MHz = Fb *1/2

Online gflorez

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Re: 6Mhz and more...
« Reply #66 on: 2017.July.12. 11:02:14 »
Can it do 20Mhz=5/4 or greater? (let's say 40Mhz=5/2)

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Re: 6Mhz and more...
« Reply #67 on: 2017.July.12. 11:12:46 »
Available multipliers are 4, 5, 6 and 8. Dividers from 1 to 65536.
Max 16 MHz * 8 = 128 MHz
Min 16 MHz / 65536 = 244 Hz ;)
« Last Edit: 2017.July.12. 11:15:53 by pear »

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Re: 6Mhz and more...
« Reply #68 on: 2017.July.12. 13:57:24 »
Very versatile, it could also be used in other projects.

Looping the loop with some ideas: The divider can be done with a rotating encoder, and the multipliers with four illuminated buttons. And a five or six characters segment screen to see the resulting frequency.... And more buttons with already defined frequencies or presets..... And... only one output frequency may be insufficient.... etc.

But wait, were not we talking about doing something simple....?

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Re: 6Mhz and more...
« Reply #69 on: 2017.July.12. 14:25:55 »
Simple is always just an idea.
When it comes to detail, it starts to complicate.
The layout for now (in my head) consists of four main components:
- microcontroller,
- PLL,
- LED display (3 digits),
- encoder (with button).
Is that a lot ?

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Re: 6Mhz and more...
« Reply #70 on: 2017.July.12. 14:59:57 »
One button is perfect, as there are only four multipliers, they can be selected sequentially. Or also be used for presets if, for example the button is pressed for more than two seconds, the saved frequencies  could be selected by the encoder.

A lot of things can be done later when programming.


One important thing, the last frequency has to be remembered on start-up to not force the user to select the frequency each time the computer is turned on.
« Last Edit: 2017.July.12. 15:05:06 by gflorez »

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Re: 6Mhz and more...
« Reply #71 on: 2017.July.12. 17:45:57 »
Easy to do, the microcontroller has an EEPROM.

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Re: 6Mhz and more...
« Reply #72 on: 2017.July.12. 18:42:14 »
Yes, but to not stress the memory so early, before saving the last value, first test if it is the same that was stored on the EEPROM.

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Re: 6Mhz and more...
« Reply #73 on: 2017.July.13. 06:39:51 »
I can store last value after power off :D Magic :cool:

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Re: 6Mhz and more...
« Reply #74 on: 2017.July.13. 09:39:24 »
Before I start.
Will there be need a second clock output for other chips/circuits (NICK, DAVE, other) ?