http://geoffg.net/terminal.html
this thing. not my creation this time, but useful. Philip kindly made a kit available to me and immediately I thought, how do I get my RS232 port back? On Wed, Feb 5, 2020 at 1:47 PM Mike Stein <mhs.st...@gmail.com> wrote: > VT100 emulator? Tell us more... > > > ----- Original Message ----- > *From:* Stephen Adolph <twospru...@gmail.com> > *To:* m...@bitchin100.com > *Sent:* Wednesday, February 05, 2020 12:04 PM > *Subject:* Re: [M100] sending fast data using modified cassette port > > exactly the motivation ;) BTW I have my VT100 emulator board running. > Tonight I hope to fire characters at it using this mod. > > > On Wed, Feb 5, 2020 at 11:55 AM Mike Stein <mhs.st...@gmail.com> wrote: > >> Neat; will have to check it out. >> >> Sounds like the perfect answer to redirecting the video to an external >> terminal/display while leaving the RS-232 port available. >> >> And if you're going to use 'real' RS-232 you'll probably have to invert >> it anyway. >> >> m >> >> >> ----- Original Message ----- >> *From:* Stephen Adolph <twospru...@gmail.com> >> *To:* m...@bitchin100.com >> *Sent:* Wednesday, February 05, 2020 10:27 AM >> *Subject:* Re: [M100] sending fast data using modified cassette port >> >> yah interesting. Almost the same approach. >> I think it is wise to take the TTL signal from the output of the schmidt >> trigger buffer, rather than from the CPU itself. So in M100 use case that >> would be inverted TTL. >> But overall, the same. >> >> On Wed, Feb 5, 2020 at 9:47 AM Kurt McCullum <ku...@fastmail.com> wrote: >> >>> Interesting Steve, >>> >>> As I was looking at that I couldn't help but think of the TTL output >>> that the NEC8201 has available on Pin 1 of the cassette port. Looks like >>> you may achieved something very similar. >>> >>> For input you could always look to the BCR port. The two could be used >>> in conjunction to create a TTL i/o pair. >>> >>> Kurt >>> >>> On Wed, Feb 5, 2020, at 4:58 AM, Stephen Adolph wrote: >>> >>> I've been toying with using the cassette port to send serial data, for >>> use with an external device that only takes input data. Kinda the opposite >>> of the BCR port. >>> >>> The point being - to save the RS-232 port for bidirectional comms. >>> >>> After some experiments, I think it is quite useful. I have been able to >>> demonstrate an absolute maximum speed of ~100kbits/sec (which isn't all >>> that useful given the typical serial port speeds) and a more useful 57600 >>> kbits/sec. >>> >>> Quite respectable! >>> >>> To use this routine, you need to make a small change to the hardware. >>> There are two unused pins on the cassette port (suggest using pin 7). >>> Install a single lead from pin 7 to pin 12 of M34. This wire bypasses >>> the analog filter used by the cassette circuit, and allows the direct >>> output of high speed signals. >>> Connection to an external device needs only 2 wires from the cassette >>> port - ground and Tx data. >>> >>> [image: cassette hack.png] >>> >>> A demonstration routine is attached that just loops and sends the same >>> character out the cassette port is attached. At the core it is a very >>> short routine. >>> Comments welcome. cheers Steve >>> >>> >>> *Attachments:* >>> >>> - cassette hack.png >>> - sndcas_57600.asm >>> >>> >>>
