Well, my holy quest for the Z800 has almost drawn to a close. As you may (or more than likely, may not) be aware, I have for many years now planned to customise the SAM by the replacement of the weakest part of the system... the CPU.. :)
[ nb 'A Z8108 internally clocked at 24Mhz linked to a 6Mhz bus'] After a strenous search of our universities' VAST library (how DO you indicate a sarcastic tone of voice on an email message?... oh, never mind..) I have finally found.. the 1983/84 Zilog Data book, with full specs on the Z800 series. wow. I can see you're all impressed already. It would appear that my earlier theory that its just a straight cut and paste job, so to speak, was ever so slightly misguided. As I suspected, the Z8108 is indeed fully pin compatible with the Z80 (weeeelll... after you rearrange and demultiplex them, anyway.. )... execept for one teeny problem. Now, if you would all care to turn to your diagrams of the Z80... (pause for the rustle of papers), you will see it has a CLK input. No surprise there. In fact, the surprise would come if... oh, never mind... I'll get on with it.... To cut a long story short, as we are all well aware the ASIC dishes out the Z80's clock signal on the SAM, and thus the ASIC basically drives the bus (not in the literal sense of the word, but it requires exact timing, hence it gives the CPU clock). Now, if I were to place a Z800, which has a clock output, and a direct crystal/oscillator input, into this system, things get messy... especially since the Z800 requires double the clock input frequency that the bus is meant to run at. So all I need now is an accurate clock doubler that feeds from the ASIC into the two crystal inputs of the Z800, and reference it against its own clock output somehow so it gives its clock signals at exactly the same time the ASIC would dish out the clock signals to the Z80...... heeellllpppp! (Any suggestions, Si...? In the interests of inter-group diplomacy, obviously.... I'm just a poor coder who doesn't know much about hardware beyond the obvious bits... :) ) DMZ -- I'm doing quite a good job of remaining anomalous, actually.... === PS Please ignore this message.... :)
