Other than the CPU, only one other component in the TRS-80 Color Computer contributes important timing: Motorola's MC6847 Video Display Generator. Just two signals from the VDG are important: /HS (horizontal sync) and /FS (field sync, also referred to as vertical sync). Both connect to CPU interrupts and so affect program execution. Each signal is a simple high/low, constant, cycle. Just these 5 pieces of information are required:
- Number of cycles the /HS line is high and low
- Number of cycles the /FS line is high and low
- How /FS timing relates to /HS
All of that information is contained within the MC6847 datasheet although I found it quite a challenge to figure out. In fact it would have been much quicker to hook up a logic analyzer and measure the timing, but not nearly as fun. Not wanting to deprive others of the same challenge, I'll just share a (mostly) readable copy of the MC6847 datasheet. If you can figure out the three pieces of information above, post your results to the comments below and I'll let you know if you are right.