8085 is a single 5 volt power version of the 8080 with the addition of 2 instructions (for shifting data in/out of chip serially) and some extra interrupt lines. The downside is the low 8 address lines are multiplexed onto the data buss. Requires one latch chip to recover the address, but that could be inside your FPGA. Z80 is 5 volt only with more interrupt modes, more interrupts, a second set of registers, WAY more instructions, and attempts to handle DRAM refreshing (but only had a 7-bit address counter so it's pretty much worthless for modern DRAM refresh). HOWEVER, when first powered up it pretty much runs like an 8080. The other interrupts are available but don't have to be used and the default interrupt mode is like an 8080 and remains that way unless told to change modes. The extra instructions and registers are available, but the Space Invaders software won't use them. The refresh counter will be running, but will just result in extra memory reads. If you really had to you could have the FPGA ignore the refresh cycles. There is one other chip by National Semiconductor, the NSC800 that is a CMOS cross of the 8085 and Z80. For your purposes, though, it would act like an 8080. Timing wise, the 8085 is the closest to the 8080. It's basically a combination of the 8080 and its clock chip with a few extensions you won't be using. pc2jamma wrote:

Hummm !!! This is a good idea !!!

I read some articles and people saying that, Z80 is "software" compatible with I8080, but I ever never see one case study.

Can you drop a few words about this ?

I have a few working board sets that I can "play" with... and I promise I'll try and post this to this group the results.

I'm now working one SRAM replacement for this board... I think I'm on the right way...

Thank you

JL

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Cópia:

Data:Sun, 24 Apr 2005 21:35:28 -0500

Assunto:Re: [Techtoolslist] SN 75365

...

Easier than that, use an 8085 or Z80.

pc2jamma wrote:

...

Hello Guys...

I'm thinking if is it possible to drive the I8080's Phase Clock 1 and 2 using a PNP transistor ? No, I'm not trying to re invent the wheel !!! I'm trying to put one Space Invaders in one FPGA IC (it's re inventing de SI), and once I'm doing this by piece, I mean, replacing board by board, I want to solve the MOS signal on ROM board.

Any ideas on how drive this signal witout the 75365 ?

Thank you !

José Luiz Martins

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