ez-z80

Terry Bendell

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Jun 22, 2022, 12:16:37 AM6/22/22

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I've been playing with this speedy little critter

https://www.tindie.com/products/circlem/min-ez-a-small-50-mhz-ez80-cased-system/

Douglas Miller

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Jun 22, 2022, 8:06:55 AM6/22/22

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Very cool. I have a MinZ-U from Circle-M. Good stuff.

I guess I have my winter project already... figure out how to use the Min-EZ Ethernet interface and port CP/NET to that machine.

Bill McMullen

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Jun 22, 2022, 9:18:08 AM6/22/22

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CP/NET over serial on the Min-eZ or eZ-Tiny should be very similar to the MinZ-U since they have the same USB interface and embedded CP/M 2.2 system. CP/NET over Ethernet will require a lot more underlying code than what's in the current BIOS.

Winter is also the season for development here in the frozen north. The Min-eZ only has the two eZ80 internal serial ports for consoles so my winter project will be to get MP/M II running on it with an Ethernet connection that supports Telnet or some other similar remote console support.

Douglas Miller

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Jun 22, 2022, 12:35:43 PM6/22/22

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On Wednesday, June 22, 2022 at 8:18:08 AM UTC-5, Bill McMullen wrote:
> ...

>
> Winter is also the season for development here in the frozen north. The Min-eZ only has the two eZ80 internal serial ports for consoles so my winter project will be to get MP/M II running on it with an Ethernet connection that supports Telnet or some other similar remote console support.

While I don't quite have your bragging-rights for winters, here in Minnesota we at least can relate.

I'm assuming this Ethernet module requires a TCP/IP stack running on the EZ80, so will be a bit of a challenge. I was thinking of placing the TCP/IP code in an alternate memory bank and calling it either by bank-switch or by interrupting into 24-bit address mode. Will need to look at how you've organized things for CP/M 2.2. Plenty of work, can't ice-skate and shovel snow all winter long...

Bill McMullen

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Jun 22, 2022, 2:48:11 PM6/22/22

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> Plenty of work, can't ice-skate and shovel snow all winter long...

True but we also have real ski hills nearby in the Rockies :-)

It's pretty straightforward on the eZ80 to switch between 64K Z80 mode and ADL mode with it's 24-bit addressing. My CP/M BIOS already does that for most of the "disk" processing and the Z80 mode CP/M BIOS within the 64K window is mostly transfer routines and allocation vectors.

My thoughts at this time are to create an ADL mode TCP/IP stack with straight forward access from Z80 mode applications such as via an RST instruction. The actual API will be as simple as possible and similar to a socket. I need to do a lot more clearing of the cobwebs but it seems to me that the primary requirements for these kinds of applications will be network reads and writes. My philosophy will be to bury as much Ethernet code as possible behind a simple API.

Douglas Miller

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Jun 22, 2022, 3:14:10 PM6/22/22

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On Wednesday, June 22, 2022 at 1:48:11 PM UTC-5, Bill McMullen wrote:
>...
>

> My thoughts at this time are to create an ADL mode TCP/IP stack with straight forward access from Z80 mode applications ...

That sounds great. The current CP/NET code (SNIOS) I have over Ethernet uses the WizNET W5500 chip, which implements TCP/IP for me. I just use TCP/IP sockets to communicate with the server (or, in the case of MP/M, the clients). So, if you provide a socket-like interface then I just need to port my W5500 code to your API. That would also give us an MP/M plugin to run a CP/NET server.

I have a JAVA CP/NET server (using sockets) that should run on nearly any modern computer (if it has a JAVA RunTime), so it provides easy access to your computers files and storage from CP/M (CP/NET).

Steven Hirsch

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Jun 23, 2022, 8:42:57 AM6/23/22

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I just ordered my min-eZ and, like you folks, are planning to concentrate on
it during the winter months (Vermont is not a tropical wonderland during that
time of the year :).

Phil G

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Jun 27, 2022, 12:00:51 PM6/27/22

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Not sure about the eZ but what most of these speed-demons lack is a 4mhz Z80 mode. This is admittedly only of interest to retro enthusiasts but a lot of the more interesting items from the CP/M archives are geared to this speed, which was an industry-standard for many years. Programs such as Richard Russell's music compiler, ham-radio related AX25, RTTY and Morse programs, samplers etc often use software delays that dont have big enough loop counters to run at 195mhz!
Cheers :-)
Phil

Randy McLaughlin

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Jun 27, 2022, 12:38:08 PM6/27/22

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The EZ-Z80 are considered "upgrades" to the Z80. Like the old V20's they are dual mode processors can run 8 bit code when switched over but are both limited to 64K of RAM. While you can add an mmu to allow the 8 bit mode expand it would add new headaches.

I prefer the FPGA approach, the mmu can be integrated into the fast design. The Z180 FPGA mmu is freely available.

The Imsai Two was going to be based on the EZ80 but design goals were lofty, and delays destroyed that project. When the Imsai Two was first suggested the Z180 was expected to be the processor.

Randy

Bill McMullen

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Jun 27, 2022, 12:41:24 PM6/27/22

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There are a *LOT* of Z80 designs out there that can be run at 4 MHz but very few that can approach 200 MHz using actual Zilog chips. Could an eZ80 be designed at 4 MHz ... absolutely and the F91 variant also includes a PLL which allows multiple frequencies via software. However neither the Z180 or eZ80 have the same T-state timing as the Z80 since the Z180 has optional versus fixed refresh states and the eZ80 is pipelined.

The Min-eZ actually uses a 10 MHz oscillator and the PLL to achieve 50 MHz. It was not designed to support retro Z80 peripherals and has no expansion bus for that. The console is on UART0 and while the second UART is supported, it's via the common USB cable to the host supporting the console.