Thanks for keeping us updated.


IIRC text LCDs tend to be based on the HD44780 LCD controller,
which also can be used with a 4 Bit data bus instead of an 8 Bit data bus, this might save some I\O pins.

Garth has a nice collection of articles on his homepage... start reading here and there.

Yes, thanks ttl. As discussed on the I/O ICs page you linked to, my workbench computer's VIA1 handles all of these things at once:

• LCD
• 5-key keypad
• beeper
• printer port
• T1 interrupts for software real-time clock and calendar with 1/100th-second resolution
• I²C port
• triggering the A/D converter (which puts the data on another VIA)
• "Abort" button (like Reset but less drastic)
• and a synchronous serial port for things like my analog oscilloscope raster-graphics display.

The circuit is shown there, although I know it's not one of the easier ones to read on my site, in spite of all the time I've spent cleaning up the scan. (It's a lot for the 3x5 sheet it's on in the little quick-reference guide.)

Two more VIAs and three ACIAs handle more I/O.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

74LVC245 is a nice chip for 5V\3.3V level translation, but I'm not sure if it's still available in DIP package.
Pinout and function is identical to the 74245, and it doesn't mind which side is 5V and which side is 3.3V.


Hmm... another idea would be trying to buy Chinese EF9345 chips at ebay.
IIRC the EF9345 just needs a 74373 (or 74573) plus SRAM for generating 80*25 of text in color on a TV... if the TV happens to have a RGB input...
But writing the software for it probably won't be fun.

SGS-Thomson Graphic Processors at bitsavers:
Datasheet for the EF9345 starts on page 14 of the PDF.

Yes, the LVC245 has 5V-tolerant inputs... and I believe that's true for all chips in the LVC family.

And, as Memblers pointed out,

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

I think the EF9345 was designed to be used in Minitel terminals.
Minitel is dead and buried by now, and of course the chip is out of production.

The built in character set of the EF9345 looks a bit like in those old SAA524x Teletext chips,
but them Teletext chips only can display 40 characters per line and AFAIK they only have I2C interface.
Bit banging I2C per software with a 6502 probably won't be fast.
Hmm... it appears, that SAA524x and SAA5050 are out of production, too: nothing at Digikey.

When buying Chinese EF9345 chips, I would suggest to try using the chip in a "write only mode",
it also might be safer to connect it to a 6522 I\O port instead of connecting it directly to the CPU bus.
Don't trust the letters and markings stamped on the chip package too much, you don't know what's _inside_ the chip.
For instance, there were faked SID chips on ebay which looked pretty different from the original on the inside.


About creatively saving I\O ports on a 6522:
When attaching something like a C64 keyboard to the computer, it's usual to have an IRQ interrupt service routine
which scans the keyboard 50...60 times per second.
Considering the picture up in this thread for attaching a LCD in 4 Bit mode to a 6522, one also could attach two 74138 chips at PB0..PB3
(data input of the LCD) for scanning a keyboard, but to be on the safe side the IRQ then should be disabled while the CPU is writing 4 Bits to the LCD,
SEI and CLI instruction might be helpful for this.

Although the very fastest I²C mode is 5MHz, most I²C devices are limited to 400kHz or 1MHz; so surprisingly a fast '02 bit-banging I²C may even need NOPs to hold it down to a speed the device can handle. I have more info on it at http://wilsonminesco.com/6502primer/pot ... ITBANG_I2C, and sample code for the circuit there at http://wilsonminesco.com/6502primer/SPI.ASM . Taking it further, Jeff's circuits at http://wilsonminesco.com/6502primer/potpourri.html#Jeff afford ways for the 65c02 to do single-cycle I/O operations.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Garth, thanks for the clarification.

I better should have said:
Writing a 40*25 page of text through I2C to a Teletext chip won't be fast...
compared to writing a 40*25 page of text into the screen memory of a PET.

There are monochrome graphics LCDs with a 320*240 resolution,
but nowaday they all seem to have something like a microcontroller already integrated.
Probably not the best solution for a secure design, but there are LCDs which have I2C, SPI or RS232.


My TTL based D04 CRT\LCD controller which I had mentioned above in the thread was able
to generate an analog monochrome video signal and to simultaneously work as a monochrome
"graphics LCD controller".

Don't remember which LCD I had used, but I think it was a bit similar to the Hitachi SP14Q006-T.
BTW: _if_ you have success in buying LCDs without a controller already integrated:
there might be no standart for the pinout, better expect the pinout of the LCDs to change once per year or so.

74LVC245 in DIP format.
I use these on 2 of my projects that connect a VIC-20 to a breadboard...

https://www.digikey.ca/products/en/integrated-circuits-ics/logic-buffers-drivers-receivers-transceivers/704?k=74LVC245&k=&pkeyword=74LVC245&pv69=80&sf=1&quantity=&ColumnSort=0&page=1&pageSize=25

Also note that these are active status by the manufacturer, one of my rules for choosing a part.
Brad