Machine language millisecond timers for the Z-80 microprocessor

Two Z-80 machine language millisecond timers for the Model III TRS-80 are presented and described: MSEC DELAY TIMER and MSEC LATENCY TIMER. The latency timer may be used with keyboard input (key release or key press) and may also be designed to respond to a signal at one of the computer’s I/O ports. The assembly language programs may be revised for other Z-80-based computers. Calibration procedures are described, and a sample two-field tachistoscope program is presented.