Appendix D - Z88 Clocks
Summary of the Z88 hardware clocks :
Gliffy Diagram is only supported by the cloud editor
Because Forge macros arent supported by the legacy editor, you'll need to convert this content to the cloud editor to display this macro properly. Find out more about converting to the cloud editorThe ratios between the Z80 clock and ticks are powers of 2 and thus directly driven by a 15 bits counter where :
bit 0 is PM1, the Z80 clock
bit 7 is SCK, the standby clock
bit 10 is the beeper
bit 14 is the 5 millisecond tick (i.e. bit 0 of TIM0)
The tick counter (TIM0 register) has a special behavior. TIM1 (second counter) is incremented when TIM0 reaches 128 (bit 7) and continues counting up to 199.
The second counter (TIM1) counts from 0 to 59 (6 bits).
Minutes registers are in fact only one large counter of 21 bits : TIM2 (8 bits) + TIM3 (8 bits) + TIM4 (5 bits).