Good point. I think I have a 512K one because that’s what I had handy – they’re used in many of the Retrobrew ECB and John Monahan’s S100 various boards. I don’t think I have any 62256 chips around, but so long as I keep handshaking disabled, we should be good. ? I will give a revised ROM a try. It’s just an extra set of steps to use, but might be a fair compromise given the very narrow use for this. ? I requested a full data sheet on the modem from the manufacturer. It uses the AT command set which is good, but it has a reset pin, so I’m looking for the required pulse width for it. RESET isn’t exposed on the Z80MC when it’s in a case – P1 on the SIO has a missing “key” pin with no hole. So, I plan on a simple RC circuit local to the modem (if needed). ? I found a text-based browser called “Links” which is like Lynx but it seems to be pure text with no DOS-graphic characters. It’s written in C, so maybe there’s a way to pare it down to a bare minimum just to parse basic HTML. Need to look at that. ? More to come! ? ? ?
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On 8/18/20, 7:35 AM, "joshbensadon via groups.io" < [email protected] on behalf of joshbensadon@...> wrote: Rich,? If you switch to using a 32K RAM on your SIO, you won't need to cut and patch any RTS/CTS traces.? Firmware is not making any use of RAM Banks. To have the system boot up to BIT only, just have a look at the ROM source code.? The preliminary boot up of this board goes through 3 steps.? 1. Why is the board booting up (answers are: cold boot, warm boot requested, unknown hardware reset?) 2. What hardware is connected (answers are FP board, SIO Board, Both or None) In this last step, on line 618, there is a call to SET_IO with the parameter of what hardware is connected. If both boards are installed, I just find it convenient to send IO to both ports so the user can't make a mistake.? If you don't want to change the ROM, I'm sure we can find a way to add this change to the Z80MC_GO program.? This way, you can simply copy a different .hex file to the SD card. Perhaps have both .HEX files and select the configuration manually with the S-Boot SD card option. On Monday, August 17, 2020, 11:54:50 p.m. EDT, Richard Cini <rich.cini@...> wrote: While on the topic of modems...
They are used in credit card terminals. 2400 baud. Only thing they need besides the normal stuff is a reset signal. Battery...Bluetooth console...dial-up modem. Just imagine the portable BBSing possibilities! I ordered a set for experimentation.
Rich
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Rich Cini
?On 8/17/20, 12:36 PM, "Lee Hart" <[email protected] on behalf of leeahart@...> wrote:
? ? Richard Cini wrote:
? ? >? ? ? ? ? ? ? ? ? Just a fun thing to do with the Z80MC and SIO card.
? ? > With some great detective work from Josh and a little bit of tinkering,
? ? > I was able to get the SIO connected to a Hayesmodem 300 and to get an
? ? > old CP/M program called “MODM221A” running. MODM221A is a derivative of
? ? > the original MODEM program from Ward Christensen.
? ? What a cool idea! I still have my Hayes Smartmodem, and fondly remember
? ? using it to log onto various BBS's on my CP/M computer back in the 80's.
? ? >? ? ? ? ? ? ? ? ? Using this combination, there are a few things to note.
? ? > First, you have to boot to the monitor and make sure that console input
? ? > is the bit-banger only, and then load CP/M manually. There’s probably a
? ? > way to permanently do this, but it would require modifying the system ROM.
? ? If anyone figures it out, I can make a new ROM. There are a number of
? ? upgrades like this that I've been meaning to get into. (Where does the
? ? time go...)
? ? > Second, since DTR and RTS are used as address bits, the ACE
? ? > initialization in MODM221 has to disable DTR and RTS (or, if those are
? ? > needed, then the RAM needs to be reduced to 32K and 5V re-routed to put
? ? > it in the right place for the 32K RAM).
? ? The 8250 has four output bits; DTR, RTS, OUT1, and OUT2. I supply a 128K
? ? RAM for U1; it only needs two extra address bits. I happened to use DTR
? ? and RTS (leaving OUT1 and OUT2 unused).
? ? In hindsight, I could have used OUT1 and OUT2 for the extra address
? ? bits; that would leave DTR and RTS free to use normally for serial
? ? communications. Maybe I can do that on the next "spin" of the board.
? ? >? ? ? ? ? ? ? ? ? I don’t have a BBS setup, but I do have all the parts
? ? > for it – a computer with a Digi 8-port serial board and an analog
? ? > telephone switch. So, that will be my next project.
? ? I wish I knew more about the modern internet. It seems like it should be
? ? possible to setup a "modern" BBS that old CP/M computers can log into.
? ? The old modem would be replaced with a "black box" that connects to the
? ? internet instead of a phone line.
? ? I've seen this done; but the "black box" is a PC, complete with keyboard
? ? and screen. In fact, you do everything on the PC itself. The CP/M
? ? computer is redundant.
? ? Then there is the question of what the web pages on the internet look
? ? like that such a "BBS" accesses. They can't be the usual HTML, color,
? ? graphics, javascript, etc. if you expect a CP/M computer to deal with
? ? it. Examples I've seen may *look* like an old time terminal (like
? ? <> ) but in fact it's a page full of the usual HTML,
? ? javascript, CSS, etc.
? ? Lee Hart
? ? --
? ? A designer knows he has achieved perfection not when there is
? ? nothing left to add, but when there is nothing left to take away.
? ? ? ? ? ? -- Antoine de Saint Exupery
? ? --
? ? Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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