see you have a Z80@20MHz (I have plenty of those). Any plan to add a turbo frequence?
I'm trying to picture out how to make one:
Code: Select all
LD r,r'
-------
M1R:T1 M1R:T2 M1R:T3 M1R:T4
|_________ |_________ |_________ |_________
PHI x 1 / \_________/ \_________/ \_________/ \_________/
|_________ | |_________ | _________
/MREQ \_____________________________/ \___________________/ \
|_________ | |________________________________________
/RD \_____________________________/
:
|____ |_________ |____ |____ :
PHI x 2 / \____/ \_________/ \____/ \____/
|____ | |____ |_________
/MREQ \________________________/ \____/ \
|____ | |____________________
/RD \________________________/
:
|__ |_________ |__ |__ :
PHI x 4 / \__/ \_________/ \__/ \__/
|__ | |__ |_____
/MREQ \______________________/ \__/ \
|__ | |____________
/RD \______________________/
:
|_ |_________ |_ |_ :
PHI x 5 / \_/ \_________/ \_/ \_/
|_ | |_ |___
/MREQ \_____________________/ \_/ \
|_ | |________
/RD \_____________________/
But for MZ-700, I see some complications: when accessing ROM ($0000-$0FFF), there is an extra /WAIT signal inserted in the normal CPU timing by the LSI so the /WAIT = 0 may indeed occur too late with the multiplied frequency. So it looks there is a need for an arbiter to generate those /WAIT signals smartly.