The Ace Place

It has been a while. Full-time paid employment means I have enough cash to finish this but limits the time I can spend finishing it. The current state of play it that I have added some SMDs to get in some practice with those. One of the SMDs is a frequency multiplier so that with the original crystal to drive the video I can vary the CPU speed from the 3.278MHz of the original ACE up to 19.668MHz and perhaps beyond. I've also made some modifications to make the KIO optional and enable full ACE compatibility. The KIOs are very difficult to get hold of and with Z84C15 and Z182 available these seem like the best CPU to be going forward. The fastest CPU I have is 20MHz and while I had to up the speed of the RAM, everything else seem happy on the CPU side. The Video was less happy, but I am not 100% convinced that was a speed problem. The multiplier I'm using on this board is a Renesas 512MLF , which is pin compatible with the On Semiconductor NB3N502DR2G , though the multiplicat...

I'm finally able to start working again after a couple of flat moves and slap bang into another wall. A Z84C90 shaped wall. I couldn't find a worked example of KIO code and the documentation is sparse. Most of the components are covered in examples for the stand-alone chips but not the KIO Command Register.  This is all you get.   I thought I was writing the register as it says it must be done put not only must you write to the registers you must have D3 set to 1 or no interrupts. KIO_INIT:     .ifdef Z84C15     .else     ld    A,01111011B    ; SIOPIA Mode = PIA, Reset SIO, Reset CTC, Reset PIO, Daisy chain write enable, Daischain = CTC,SIO,PIO     ld    BC,KIOCMDA     out    (BC),A     .endif