H8-Z80 V4 construction

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Les Bird

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Aug 25, 2021, 11:25:55 AMAug 25
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Hi all,

Been a while since I've been into building PCBs. Prepping for the V4 motherboard which is asking for a 16.384Mhz oscillator. On eBay I found a 10 pack of VCXO full can oscillators and ordered it. Not knowing exactly what VCXO stood for I looked it up and now I'm wondering if it will work with the V4 board. Can someone shed some light? I don't remember VCXOs being a thing back in 2009 when I was heavy into building PCBs.

Also, what's the 10 Mhz oscillator for? I ordered some from Mouser but now they say they're out of stock, not sure if I got my order in before that happened.

I am not planning on building out the RTC portion of the board.

Les

Glenn Roberts

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Aug 25, 2021, 11:35:04 AMAug 25
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The board has room for both oscillators but you only need one. I have the 10 mhz one. When i select "max speed" the board runs at 10 Mhz. Ive never tried 16. As i recall theres a jumper to select which oscillator to use

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Norberto Collado

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Aug 25, 2021, 12:03:34 PMAug 25
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Z80 Max speed can be 10MHz or 16MHz. Currently the Z67-IDE+ can do 10 MHz when booting from it. With the SSI board installed the Z67-IDE+ can do 16MHz without any issues. For now select 10MHz via jumper. If you need a 10MHz oscillator let me know.

 

Norby

Norberto Collado

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Aug 25, 2021, 12:10:14 PMAug 25
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Voltage Controlled Crystal Oscillator (VCXO) or Voltage Controlled Oscillator

VCXOs incorporate a control voltage pin that controls the output frequency around the nominal frequency. The extent of frequency control is called the pull range which typically ranges from ±50 ppm to ±200 ppm but can extend to ±3200 ppm for SiTime VCXOs. VCXOs are often used in discrete jitter attenuation and clock recovery applications.

Steven Feinsmith

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Aug 25, 2021, 12:36:03 PMAug 25
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A crystal oscillator is an electronic oscillator circuit that uses the mechanical reverberation of a vibrating crystal (typically a quartz crystal) to create an electrical signal with precise frequency. TCXOs use an element known as a voltage-controlled crystal oscillator (VCXO).

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From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Les Bird <les...@bellsouth.net>
Sent: Wednesday, August 25, 2021 11:25:55 AM
To: SEBHC <se...@googlegroups.com>
Subject: [sebhc] H8-Z80 V4 construction
 

Peter Higgins

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Aug 25, 2021, 7:01:54 PMAug 25
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The "Bill of Materials" for this board tells you exactly where to find all the parts, and though most can easily be obtained from multiple sources there are a few parts that are "hard to find". Web links are provided for all parts this board requires, but referring specifically to the two crystal oscillators you asked about:
U110 10MHz half can TTL oscillator - Jameco part number 102779 - many still in stock @ $1.75 each
U116 16.384 full can TTL oscillator - as mentioned in the BOM, not an easy part to find. Tayda part number A-725 - many still in stock @ $1.29 each


On Wednesday, August 25, 2021 at 8:25:55 AM UTC-7 Les Bird wrote:

Been a while since I've been into building PCBs. Prepping for the V4 motherboard which is asking for a 16.384Mhz oscillator.

Les Bird

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Aug 25, 2021, 7:17:37 PMAug 25
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Thanks all,

Norberto, the Mouser oscillators did ship today so I have some 10Mhz on the way. Thank you for the offer to send one.

Good to know that I can choose which one to use.

Also, another question - what are the 1.8432 and 3.68Mhz oscillators used for? When I remade the H8-4 I used a 1.8432Mhz oscillator as the clock but based on the layout of the board it looks like the 3.68Mhz is used for the DUART.

Les

norberto.collado koyado.com

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Aug 25, 2021, 7:32:11 PMAug 25
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The Z80 V4.0 provides the capability to integrate additional baud rate generators oscillators for high-speed connections over network for specific user needs. ROM/OS changes will be needed.
  • U113 - 1.8432MHz - for 115.2K baud. Jumper selectable (Heath default)
  • U4 - 3.68MHz - for 230.4K baud. Jumper selectable
  • X1 - On DUART module - 14.7456MHz - for 921K baud. Jumper selectable
This board offers more options for higher baud rates. For stock HDOS or CP/M, then use 1.8432MHz osc.

Hope this helps,
Norby



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Les Bird

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Aug 25, 2021, 7:39:01 PMAug 25
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Ah, awesome. Thanks Norby, very helpful to know that.

Les

Gery Kissel

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Aug 25, 2021, 7:53:39 PMAug 25
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Hey Les,
I hope you enjoy building the V4 as much as I did!
Gery

Les Bird

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Aug 25, 2021, 8:09:17 PMAug 25
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Gery, it looks like a lot of fun. I think I will. Your board looks like it turned out really well and looking over your thread I see that I need to pay close attention to the orientation of some of the parts.

Les

Les Bird

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Sep 2, 2021, 5:43:46 PMSep 2
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Hi all,

An update to my V4 build.

I didn't have all the parts to build the V4 board so I decided to build out the V3.1 board, which I had all parts for. For the life of me no matter what I did I could not get the V3.1 board to boot up. I built only the parts of the board that I decided to use so I built it with the 10Mhz oscillator and left out the 16.384Mhz one, as I had no plans to run it that fast. After an email to Norberto he explained that the 2Mhz clock signal for the CPU comes from the 16.384Mhz oscillator, and now that I think about that it makes total sense - you can't divide 10Mhz down to 2.048Mhz but you can do that with 16.384Mhz. So after plugging in a 16.384Mhz oscillator the V3.1 board booted right up.

We should definitely have a Wiki somewhere with all this information in it - such as, what components are needed and not needed depending on what you need from the board in addition to trouble shooting tips. Anyone know where we can host a Wiki page?

V3.1 up and running.

Also, the top 7805 regulator gets super hot whereas the bottom one is not even warm. All chips are cool to the touch. Is this normal?

Les

norberto...@koyado.com

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Sep 2, 2021, 10:20:37 PMSep 2
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Also, the top 7805 regulator gets super hot whereas the bottom one is not even warm. All chips are cool to the touch. Is this normal?

 

Yes it is normal. Please attached both regulators to the H8 heatsink bracket or add a heatsink under them. I have mine attached to the H8 heatsink and on my other board I use the Pololu regulator to eliminate the heat.

 

Do not leave the regulators without any heatsinks.

 

Glad that the board is fully functional. It is a great board.

 

Thanks,

Norberto

norberto...@koyado.com

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Sep 2, 2021, 10:59:51 PMSep 2
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Here are some examples:

 

Terry’s solution: It comes with the caps.

 

 

 

Pololu Reg: These days are very expensive

 

 

Flat bracket: 7805

 

 

Regular H8 bracket: 7805

 

image007.png
image002.jpg
image004.jpg
image006.jpg

Les Bird

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Sep 5, 2021, 2:09:58 PMSep 5
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All (Norberto),

Trying to boot H17 disks with the V3.1 board. When I press 2 on the keypad to boot H17 it doesn't work, it activates the drive and seems like it is trying to boot but it fails. It then re-seeks and tries again. After 3 tries it gives up and beeps. I'm booting CP/M 2.2 on 3.5 via HSFE. If I swap out the board with a DG80 with XCON8 then it'll boot fine. So the HSFE and drives and disk are working. I'm using the PAM37/MMS ROM on a 27C256 that Norberto sent me a while back.

I know I'm way behind the times here so maybe this was solved a while ago.

Any ideas?

Thanks!

Pic below to show jumper settings

IMG_6519.jpg

Norberto Collado

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Sep 5, 2021, 2:26:24 PMSep 5
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Hmmm… Just change the following jumper to find out if it does helps out. I think you are using position 1-2. Try position 2-3 on JP6 in case the H17 sides are reversed.

 

Norberto

 

 

All (Norberto),

 

Trying to boot H17 disks with the V3.1 board. When I press 2 on the keypad to boot H17 it doesn't work, it activates the drive and seems like it is trying to boot but it fails. It then re-seeks and tries again. After 3 tries it gives up and beeps. I'm booting CP/M 2.2 on 3.5 via HSFE. If I swap out the board with a DG80 with XCON8 then it'll boot fine. So the HSFE and drives and disk are working. I'm using the PAM37/MMS ROM on a 27C256 that Norberto sent me a while back.

 

I know I'm way behind the times here so maybe this was solved a while ago.

 

Any ideas?

 

Thanks!

 

Pic below to show jumper settings

 

 

Les Bird

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Sep 5, 2021, 2:34:12 PMSep 5
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BINGO! That was it.

Norby, I can't express how grateful I am (we are) to have you on our team. You are so helpful and knowledgable and with just a vague description of a problem you know exactly how to fix it.

Thank you!

Les

Norberto Collado

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Sep 5, 2021, 2:42:07 PMSep 5
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Great that it worked. This is the schematic for such circuit. We will need to update the jumper description when using the Heath H17 controller vs my H17 controller which uses position 1-2. Great catch.

 

Diagram

Description automatically generated

 

Thanks,

Norby

 

BINGO! That was it.

 

Norby, I can't express how grateful I am (we are) to have you on our team. You are so helpful and knowledgable and with just a vague description of a problem you know exactly how to fix it.

 

Thank you!

 

Les

 

On Sunday, September 5, 2021 at 2:26:24 PM UTC-4 Norby wrote:

Hmmm… Just change the following jumper to find out if it does helps out. I think you are using position 1-2. Try position 2-3 on JP6 in case the H17 sides are reversed.

 

Norberto

 

Image removed by sender.

 

All (Norberto),

 

Trying to boot H17 disks with the V3.1 board. When I press 2 on the keypad to boot H17 it doesn't work, it activates the drive and seems like it is trying to boot but it fails. It then re-seeks and tries again. After 3 tries it gives up and beeps. I'm booting CP/M 2.2 on 3.5 via HSFE. If I swap out the board with a DG80 with XCON8 then it'll boot fine. So the HSFE and drives and disk are working. I'm using the PAM37/MMS ROM on a 27C256 that Norberto sent me a while back.

 

I know I'm way behind the times here so maybe this was solved a while ago.

 

Any ideas?

 

Thanks!

 

Pic below to show jumper settings

 

Image removed by sender.

 

On Thursday, September 2, 2021 at 10:59:51 PM UTC-4 Norby wrote:

Here are some examples:

 

Terry’s solution: It comes with the caps.

 

Image removed by sender.

 

 

Pololu Reg: These days are very expensive

 

Image removed by sender.

 

Flat bracket: 7805

 

Image removed by sender.

 

Regular H8 bracket: 7805

 

Image removed by sender.

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