When I acquired a KIM-1 Rev A, obviously sold by NCE/Compumart, it came with some documentation that may interest any programmer working with the MOS Technology (R)RIOT 6530 and 6532.

The timer description the datasheet is a bit vague about how to use. What may help is the document ‘KIM-1 Application Note 2 Interval Timer Operation’ by MOS Technology.

A document with listings of KIM-1 programs called ‘KIM-1 Application Programs CT1’ illustrate the usage of the timer in interrupt mode. You find the documents here:
Compumart KIM-1 Rev A – Retro Computing