I put together a Z80 microcomputer the other day. Real simple: processor, clock oscillator, NVRAM holding program and data, pair of
74LS138s for memory and I/O decoding, and two 74LS273 latches for output. And a forest of jumper wires. Right now I have it scrolling a message across four matrixed digits of seven-segment display. Seven segments make really ugly Latin characters though. :-(
Nice, I just picked up a Kaypro for free. When I get around to it I'll power it up. A nice display for your project would be one of those serial driven
Bet I had the most innovative use of a Z80 back in the 80s It was a // printer buffer that could do auto landscape /portrait flip...The innovative bit was the memory.... 8x64K dram chips hung directly on the address bus with /ras/cas driven by I/O control lines. Memory access was I/O mapped(effectively) and something like 10 instrucions per byte to access. Happy days :)
On a sunny day (Fri, 30 Jan 2009 09:34:04 -0000) it happened "TTman" wrote in :
That was not so innovative as you may think, as I did the same with IO mapped RAM disk: The diagram of bus interface, with actually a write protection flipflop, that needs to be set before any writes: ftp://panteltje.com/pub/z80/ramdisk-1.jpg
The diagram of the 8 256 kbit DRAM chips soldered on top of each other: Note on how I use the clock signal to cycle the row address for refresh when no data is being accessed. ftp://panteltje.com/pub/z80/ramdisk-2.jpg
The system worked by loading a 5 1/4 inch single sided Kaypro2 disk into the
256 kbyte DRAM, making it the fastest Z80 on the planet (all disk IO now DRAM).
Picture of the RAMdisk board, it all has become very dusty, just digged it up from the attic, the tape I pealed away, it protected the RAM chips: ftp://panteltje.com/pub/z80/ramdisk_top.jpg
This one is pure art! ftp://panteltje.com/pub/z80/graphics_card_top.jpg
And this one is the other side of it, the power routing: ftp://panteltje.com/pub/z80/graphics_card_bottom.jpg I think this one dates about 1984 or so.
Of course any self respecting computer has a sound card too: ftp://panteltje.com/pub/z80/soundcard_top.jpg ftp://panteltje.com/pub/z80/sound_card_bottom.jpg It has as experiment putting the caps and resistors in IC sockets. That actually worked so well I repeated that in a much later design.
I like the Z80 and 8051. They are very nice processors. Is the CDP1802 available as a free core? Now there's a nasty processor if there ever was one.
I refuse to design it in so the rest of you are safe.
For those who don't remember: I have a 100% hit rate on every CPLD or other FPGA like part I design in going out of production. So as a service to others I have decided never to design in a device like that from a company that I wish to have remain in business.
I wouldn't use an 8051 when more modern architectures are around. The advantage of having the cpu in the fpga is that you get a lot of speed and save a lot of pins.
We've been considering going to a new Coldfire processor, with all sorts of chip selects, dram controllers, timers, stuff like that. But if we get an FPGA with an ARM inside, the peripherials all just become adaptable chunks of FPGA, so if we want 17 timers, we get 17 timers. Or maybe a cpu with 231 parallel port pins.
Yup, the fpgas are great for brute parallel processing. But they're also great when you just need a lot of counters and latches and port pins, quantities of dumb stuff.
Ah, the venerable Z80. I have a handful of them and their various peripheral chips. e.g. DMA. My first uC project was an EPROM burner made with 2MHz (raw power!) Z80. I still have it but haven't used it in years because ..... well, I haven't had to burn an EPROM! EEPROM is so much nicer to work with.
In article , snipped-for-privacy@highNOTlandTHIStechnologyPART.com says...>
Yep. I'd kinda like a DSP in there though. It seems a waste of high speed logic to do the function our DSP is now doing (and it works), but saving pins would be a big bonus.
Yep. Our current design is a mess of SPI and I2C stuff that could easily be swept into a small FPGA. FPGAs (and CPLDs) are cheap now too. Hardly any reason for small junk and glue logic anymore. The new PSoC stuff from Cypress looks interesting too.
Nobody makes a 100-channel DAC, but it's not hard to put 100 delta-sigma DACs into a small FPGA. I think you could make a decent ADC, too; most lvds inputs are actully good comparators.
FPGAs pipeline design a lot, too. You don't have to design the logic until the PC board is out for fab and assembly. And changes take hours, no board spins, no red jumper wires.
It's really liberating to have 100,000 gates laying around at an incremental use cost of zero.
Interesting idea. We have a dozenish audio channels, using six Burr Brown TLV320s. It sure would save a pile of grief to sweep those under the rug too. The Cypress chips look like they'd sweep in a whole log of the external analogs up to the howland pumps and hybrids.
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