Z80 Question for the Hardware Gurus

[airship]

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# 20MHz ZiLOG eZ8 microprocessor soft core
# 64KB Flash program memory
# 4KB register RAM
# 12-channel 10-bit A/D converter
# Four 16-bit timers with PWMs and capture and compare
# Watch-Dog Timer
# 46 general-purpose I/Os
# 24 vectored interrupts
# Power-on reset and voltage brown-out
# Full-duplex SPI, I2C, and 2 UART ports with IrDA encoder/decoder
# 3-channel DMA controller
# On-chip debug with break and trap capability,
# Single-pin Flash programming
# 3.0 to 3.6 operating voltage
# Standard (0 to 70) and extended (-40 to 105) temperature range
# 64-pin LQFP and 68-pin PLCC packages

http://www.zilog.com/productserver/ss2.asp?fam=8bit

So... will somebody smarter than me (most of you, I'm sure) explain why you couldn't take one of these new, high-powered 8-bit Z80 chips and design a module to replace the Z80 in the C128, effectively turning that do-nothing-but-boot chip into a 100% compatible, 5MHz-internal, CP/M-running, coprocessor/multi-timer/4K-of-dedicated-RAM/DMA controller thingie? Thank you.

It seems to me that you could add ALL of the following features to the C128 with one of these:
# Ethernet interface w/TCP/IP stack
# IrDA infrared communications
# RS232 x 2
# Real Time Clock
# DMA controller for big internal REU
# I2C fast serial sensors/EEPROMs
# IDE controller
# etc.
AND the thing has its own on-board, program-in-place flash and a big chunk of its own dedicated RAM (up to 64k). It just seems so cool.

[zeke1312]

Probably clocking with existing motherboard and components including I/Os.

[airship]

Well, this thing is basically a self-contained computer. It's got its own RAM, ROM, and I/O. It's much, much faster than the C128, so it can get a lot done while its waiting for its opportunity.

I figure you program its EPROM with all of its own stuff, plus a bit of code for the C128. When it boots (since it has control) it checks first for a CP/M disk. If it's not there, it copies a bit of 6502 code to RAM, along with a wedge for the 6502 to see it. Then you give it an occasional peek at RAM, say during the vertical retrace when the VIC isn't particularly active. It checks a flag (or a dozen flags) to see if the C128 wants anything.

If the C128 wants a STASH, SWAP, or FETCH from the REU it controls via DMA, it does that. If the C128 wants to load from or save to the IDE disk, it does that. And so on for the RTC, RS232 buffers, TCP stack, IrDA, whatever. I don't know if you'd need a swap area in RAM for some operations; you might. For anything timing critical, the Z80 could freeze the C128 for a couple of clock cycles while it was taken care of, though I can't imagine what that would be.

Shoot, you could even use it as a math coprocessor, either for the C128 or for the VDC or VIC, which would be way cool for 3D graphics, raytracing, fractals, etc.

[zeke1312]

Could be. I'm just thinking if the new chip was back compatible to the Z80 it would probably be stated in the specifications. Generally and even though the new processor has many on-board functions, it still needs to interface with the rest of the system and clocking/timing among other things is critical in making it compatible. Other than that, I have no evidence that it would not work!

[swordfish1030]

( just dreaming... )

[Guest]

If only we could talk C= Int'l into making all of the MOS designs public so we could get Bill Mensch to do this with the 8502.  We could have a modern 128 that wasn't some FPGA hack, but would be the actual circuitry shrunk down to a single chip.

[airship]

I can't imagine there's any commercial value in the old MOS chips anymore. You do see a 6522 or 6502 once in awhile in a controller (or arcade game) that is still functioning, so there are places that sell them as repair parts, but no one is using them in any new designs. I'm 99% sure that no one even makes them anymore. Does CCI even have the design documents on file anywhere?

Zeke, these new Z80-based chips are so versatile and programmable that if there were timing issues, you could just program them away by adjusting the I/O pin timing on-chip. I think it would be a cool project, but I don't have the knowledge to even begin to approach it. I do little bits of 6502 M/L and play around with BASIC Stamps, but that's about it.

Like I've said before, I'm more of an idea man.

[Guest]

Airship

WDC (Western Design Center) is still being run by Bill Mensch and he's pumping out new 65816 based products all the time.  He even has a 6502 based computer on a board, but it's very expensive (about $300).

[airship]

D'oh! I knew that but forgot about it for the purposes of that last post.

As Emily Latella used to say on Saturday Nite Live, "Oh! Well, that's completely different! Never mind!" :förvånad: