Brings back fond memories.
My second job in Silicon Valley was manager of Zilog's training and education department (all of five of us) and taught customers how to design systems around the Z80 which included the CTC.
see: <a href="https://steveblank.com/category/zilog/" rel="nofollow">https://steveblank.com/category/zilog/</a>
Note: This is not about the Z80 CPU. This is about the Z80-CTC ship: “<i>The Z80-Counter Timer Circuit (CTC) is a programmable, four channel device that provides counting and timing functions for Ihe Z80-CPU.</i>”