M238 Synchronous Up/Down Counter

Summary: The M238 is an 8-bit synchronous up/down counter module comprised of two DEC74193 integrated circuits. It is utilized within the FP15 Floating-Point Processor (specifically in the EPA, DIR, and DAR registers). Key features include:

• Operation: Uses master-slave flip-flops triggered by positive-going clock transitions. Counting direction is controlled by separate up and down clock inputs.
• Control: Supports data presetting via load inputs (when low) and provides an independent clear function.
• Cascading: Features borrow and carry outputs to allow multiple counters to be connected for larger bit-depth operations.
• Application Note: In the DIR register, the up-count function is inhibited, restricting the unit to decrement-only operations.