I think I understand the EEPROM trick, with my poor mechanical engineer brain. If my two months of digital logic self-study are correct, you're making a chip with several state machines programmed into it, where the S-100 address lines connected to the 4 EEPROM lines select which state machine is in operation and the counter goes through the steps to output the corresponding sequence to I2C to send the data. A neat trick.
On Tuesday, March 4, 2014 2:14:47 PM UTC-8, Vince Mulhollon wrote: > > On Sunday, March 2, 2014 11:52:02 PM UTC-6, monahanz wrote: >> >> I have not found any individual OLED displays that latch and display Hex >> codes. >> > One (e)eprom with some peculiar programming and a 8-bit or 16-bit free > running binary counter driving the LSB of the address leads and a latch > sample input driven from D0 of the eprom and D1 drives the reset of the > otherwise free running counter. The MSB of the eprom address is the data > output from the latch, probably just a couple bits. The D2-D7 (however > many needed) blindly holler out I2C or SPI signals, sure hope there's a LCD > there to listen. At the end of the blindly hollered out canned SPI/I2C > message you clear D0 for awhile to latch in the new MSB for next cycle, and > then whack D1 after some time to start the whole madness over. > > Some displays get all wound up about getting initialized / reloaded over > and over. Of course if you've got the dough, just use a bigger eeprom and > slower clock, assuming you can tolerate the latency, so it only reloads the > display once a second or whatever seems about right. > > Takes a modest sized (e)eprom, a chip or two for the 8 or 16 bit counter, > a latch, and not much else.... pull up resistors for the I2C I guess, > along with the LCD (or OLED in this case). > > I would suggest that the smarter the device, the harder it is to pull this > crazy design off. > > I've done this with one message using an old LCD a long, long time ago. > Only needed 4 chips and an oscillator and made a LCD display say "hi". > > Filed under dumb eprom tricks, I guess. Its a derivative of the old "hook > up a D/A to generate sounds" trick. Works well if you only need a couple > sounds. > > Now a days you'd probably use a 75 cent custom programmed PIC. I think > this could get away with the 8 pin dip 10F series if you use I2C thats 2 > pins and 4 pins of input data and 2 pins for power and use the internal > clock. > -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
