>Anyway, almost all instructions are just rounded up to the next multiple >of 4. A few take 4 extra. Anyone who tells you that "LD A,7" takes 9.3 >cycles is obviously lying. :-)
Okay... well, I'm getting the ASIC documentation from Bruce Gordon with the week (yep, that's right - the full documentation of how the ASIC works, as done for Maplins when they were interested in buying up Bruce's old stock)... with a bit of luck, that'll explain it all. Interesting note: On hacking at the 1Mb board I've got, it uses the CPU CLK line and the REFRESH line to update the contents of the DRAMs... now, there's a whopping great GAL on that board... so, what I reckon is that the CPU CLK line is being used to generate CAS/RAS timing for memory reads, and the REFRESH line is being used in conjunction with it to produce the necessary refresh signals... Anyone got a >6MHz storage scope who can back me up on this one? :) Other hardware notes (just for amusement factor): The ASIC is decoupled from the Z80 bus by a bank of 470ohm resistors... and its bus is tied low. The Z80's bus, however, is tied high... what this means is that: 1) unfortunately, you can't really read the ASIC's output from the back of the SAM unless you tristate the Z80 -- and even then, I'm not sure if the ASIC has enough pulling power to drop the data lines enough. 2) it's possible to override what the Z80 sees when it reads one of the ASIC's ports... or even when it reads memory..... soooo..... Hardware 128k speccy emulator anybody??? :) :) :) Simon ps the forthcoming accelerator design may incorporate a ... you guessed it ... 128k spectrum emulator. Neat, huh? +- Email:[EMAIL PROTECTED] ---- Fidonet: 2:250/124.2 (Simon Cooke) -+ | Snail:1 Dovey Close, Astley, Tyldesley, Manchester, M29 7NP, UK | | Tel: (01942) 886084 Fax: (01942) 886084 (ring voice first to confirm!)| +- WWW: http://jumper.mcc.ac.uk/~simonc ----------------------------------+ ANNOUNCING the Your Sinclair WWW Archive: http://jumper.mcc.ac.uk/~simonc/ys Warning: Currently under construction in some places
