Clock generator for TF360 rev 1

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Higgy
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Re: Clock generator for TF360 rev 1

Post by Higgy » Mon Sep 09, 2019 1:08 pm

New ROM - as in change the Kickstart chip? This could also lead into issues. I can imagine there are users who will not feel confident in pulling the chip and replacing it.

If it could be done with jumpers etc, I expect only 3 speeds are needed. 50Mhz - all 060 will work. 75/78Mhz - your Rev 5/6's and 100Mhz-Balls out :lol:
2 speeds I am sure would satisfy +90% of users.

Would using NVRAM mean the TF360 would not fit big box AMIGAs. I thought I read that with an adaptor card the TF360 would/could fit into a A4000 relatively easily.

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Re: Clock generator for TF360 rev 1

Post by terriblefire » Mon Sep 09, 2019 1:46 pm

alenppc wrote:
Mon Sep 09, 2019 12:27 pm
terriblefire wrote:
Mon Sep 09, 2019 10:23 am
I’m balancing this against the sodomization that will occur to boards if end users have to do smd soldering to change speed.
How about adding a few jumpers instead?
Jumpers eat lots of board space. The CD32 is quite cramped. I’m literally thinking a port you poke to set the jumpers. Actually makes my life easier to do that and means you can set the speed depending on your application. Jumpers would need pull ups too. More components.

The module would read a byte from nvram and poke that port. It’s not an actual necessity either.
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Re: Clock generator for TF360 rev 1

Post by terriblefire » Mon Sep 09, 2019 1:55 pm

Higgy wrote:
Mon Sep 09, 2019 1:08 pm
New ROM - as in change the Kickstart chip? This could also lead into issues. I can imagine there are users who will not feel confident in pulling the chip and replacing it.

If it could be done with jumpers etc, I expect only 3 speeds are needed. 50Mhz - all 060 will work. 75/78Mhz - your Rev 5/6's and 100Mhz-Balls out :lol:
2 speeds I am sure would satisfy +90% of users.

Would using NVRAM mean the TF360 would not fit big box AMIGAs. I thought I read that with an adaptor card the TF360 would/could fit into a A4000 relatively easily.

I can’t get 200Mhz crystals easily. So I need some kind of clock generator. Once I’m there there are usually 3 control pins. I may as well do that from the CPLD. Those pins are tri state. They have 3! (0v, 1.6 and 3.3V) Values per pin so jumpers don’t work. Or at least 6! Are needed.. too many.

The nvram is optional and it would read via a library anyways... and the TF360 is going to need different firmware for the A4000 anyway.

The idea is the machine ALWAYS boots at 50Mhz before being turned up to 11 if needed.
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Re: Clock generator for TF360 rev 1

Post by exxos » Mon Sep 09, 2019 1:56 pm

Have you considered the "resistor set oscillator" from linear-tech ? I used them on my 060 CPU. Can set them between 50MHz - 100MHz etc depending on resistor value. May even be possible to change the resistor value with a couple of outputs from a PLD.

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alenppc
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Re: Clock generator for TF360 rev 1

Post by alenppc » Mon Sep 09, 2019 2:18 pm

If you go with software selectable frequency, I would avoid storing the setting in nvram for 2 main reasons:

1) It's more work+potentail maintenance for you.
2) It's not really necessary to have it stored. If you have a software-configurable clock setting, you can simply invoke it from startup-sequence at each boot.

Just my 2 cents... to keep it as simple as possible.

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Re: Clock generator for TF360 rev 1

Post by terriblefire » Mon Sep 09, 2019 2:22 pm

exxos wrote:
Mon Sep 09, 2019 1:56 pm
Have you considered the "resistor set oscillator" from linear-tech ? I used them on my 060 CPU. Can set them between 50MHz - 100MHz etc depending on resistor value. May even be possible to change the resistor value with a couple of outputs from a PLD.

https://www.analog.com/en/products/ltc6905.html
I will take a look thanks.
alenppc wrote:
Mon Sep 09, 2019 2:18 pm
If you go with software selectable frequency, I would avoid storing the setting in nvram for 2 main reasons:

1) It's more work+potentail maintenance for you.
2) It's not really necessary to have it stored. If you have a software-configurable clock setting, you can simply invoke it from startup-sequence at each boot.

Just my 2 cents... to keep it as simple as possible.
If you don’t have some kind of nvram solution then there is no way to set the speed of the CPU if you boot to CD. It could happen down the track rather than right away.

It’s a pretty simple thing though. Read a single byte from NVRAM and write it to an address in config space.
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Re: Clock generator for TF360 rev 1

Post by terriblefire » Mon Sep 09, 2019 5:55 pm

Let me elaborate a little bit more here...

I would create an 64k autoconfig device which appears as product code 200 or something. It will have a register inside it that i can poke to set three output pins on the CPLD.. This is really basic stuff. its like switching on 3 LEDs from a memory write.

These pins are connected to a PLL frequency generator. They control the frequency of the PLL as a multiplier of a 25Mhz clock.

So a 4x multiplier gives 100Mhz which would give a 50Mhz CPU. This would be reset to the default every time the RESET line goes low.

Draw a line there and say that is phase 1. At this stage you can poke a location and/or just set it with a firmware update.

But you can then create C app in 20 seconds to do this poke for you and set the speed.

Call this phase 2.

You can then wrap this up in an a library to reset it from nvram... well not specifically nvram. Whatever nonvolatile.library provides as backend storage. Its very very simple and tiny. The device/library would open nonvolatile.library, read the entry called TF360, write the byte to the TF360 config register and exit. its about 20 lines of C.

Call this phase 3.
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Maximilian
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Re: Clock generator for TF360 rev 1

Post by Maximilian » Tue Sep 10, 2019 3:17 pm

terriblefire wrote:
Mon Sep 09, 2019 5:55 pm
I would create an 64k autoconfig device which appears as product code 200 or something. It will have a register inside it that i can poke to set three output pins on the CPLD.. This is really basic stuff. its like switching on 3 LEDs from a memory write.
This would be awesome, if you have a few extra bits in NVram and a few extra CLPD pins connected to a connector with overvoltage protection this could be a really nice feature!!
(I was thinking about this for another project)
:excited:
How would you reset the NVram if the processor doesn't want to boot at that frequency?, a jumper check?
A firmware flash would be difficult for some users.

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Re: Clock generator for TF360 rev 1

Post by terriblefire » Tue Sep 10, 2019 4:29 pm

Maximilian wrote:
Tue Sep 10, 2019 3:17 pm
How would you reset the NVram if the processor doesn't want to boot at that frequency?, a jumper check?
A firmware flash would be difficult for some users.
Pull the card out... go to the boot menu and delete the entry... maybe?
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Maximilian
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Re: Clock generator for TF360 rev 1

Post by Maximilian » Tue Sep 10, 2019 7:31 pm

Makes sense, thanks for explaining.

It's a shame that it would not directly port over to other TF boards because they would need a machine with NVram too.

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