Keithley CTM-10 Counter / Timer Board

The Keithley CTM-10 is a counter/timer board for ISA-bus compatible PCs delivering precision timing and counting across frequency measurement, pulse width analysis, event counting, and pulse generation. Built around two Am9513A counter/timer chips, It has ten independent 16-bit counters capable of up to 7 MHz input rates with 70 ns minimum pulse width resolution. The board integrates selectable 1 MHz or 5 MHz onboard time bases (±0.01% accuracy, 0–70°C), software-configurable gating, input/output polarity control, and complex pulse generation. All ten counters link software-selectively to form 32-, 48-, 64-, or 80-bit counters. An 8-bit latched digital input port and 16-bit latched digital output port (LSTTL compatible) support AT/XT interrupt logic with software-selectable levels (3, 5, 7, 10, 11, 15) and jumper-selectable fallback options (2–7). Independent interrupt handling across the board's two 5-channel halves, combined with Load and Hold registers per counter, enables deterministic automated test integration.

Technical Specifications

Ten 16-bit counters (two Am9513A chips)

Maximum input frequency: 7 MHz

Minimum pulse width: 70 ns (high and low)

Onboard time bases: 1 MHz or 5 MHz at ±0.01% accuracy (0–70°C)

Counter modes: Up/down, binary or BCD

Linked counter formation: 32-, 48-, 64-, or 80-bit configurations

Load Register and Hold Register per counter

Input Low: 0.8 V max (1 mA max input current)

Input High: 2.2 V min (−10 µA max input current)

Output Low: 0.4 V max @ 3.2 mA sink; 0.5 V max @ 8.0 mA sink

Output High: 2.4 V min @ −200 µA source

Digital outputs: LSTTL compatible

Key Features

Software-selectable active-high or active-low counter inputs

Programmable hardware or software gating

One-shot or continuous output modes with retriggering

Programmed frequency output capability

8-bit latched digital input port

16-bit latched digital output port

Independent interrupt logic for each 5-channel half

External interrupt input with latching on rising edge

Interrupt level selection: software (3, 5, 7, 10, 11, 15) or jumper-selectable (2–7)

Typical Applications

Automated test system integration

Data acquisition setups

Precision frequency and pulse width measurement

Event counting and logging

Programmable waveform generation

Compatibility & Integration Designed for ISA-bus compatible PCs including EISA and Pentium-based systems.