The AcPC424 provides 24 differential input/outputs, 16 TTL input/output channels, and four 16-bit multifunction counter/timers. The 16 TTL input/output channels can be programmed as inputs or as outputs on an individual channel basis. The 24 differential input/output channels are programmed as inputs or outputs on an 4-channel port basis. All input channels can be enabled for change of state, low, or high level transition interrupts. This module saves money and CompactPCI slots by combining differential I/O, TTL I/O, and counter/timer functions on one card. Four 16-bit multifunction counters/timers can be configured for pulse width modulated output, watchdog timer, event counter, frequency measurement, pulse width measurement, period measurement, or one shot pulse output. The four 16-bit counters can also be configured into two 32-bit counter/timers.

Differential Digital I/O

I/O channel configuration: 24 bidirectional differential signals. Direction is controlled as a 4-channel group. Differential driver output voltage with 50 ohm load: 2V minimum, 5V maximum. Common mode output voltage: 3V maximum: Minimum input resistance: 12K ohms. Termination resistors: 120 ohm termination resistor networks are installed in sockets.

TTL Digital I/O

I/O channel configuration: 16 bidirectional TTL transceivers with direction controlled independently (shared as counter/timer control signals). Reset/power-up condition: All channels default to input.

Digital Input

Input voltage range: 0 to 5V DC. Input signal threshold, low to high: 3.5V typical. Input signal threshold, high to low: 1.5V typical.

Digital Output

Output voltage range: 0 to 5V DC. Output ON current range: -32 to 32mA. Output pullups: 4.7K ohm socketed resistors.

Input Interrupts

40 channels of interrupts are available for high-to-low, low-to-high, or any change-of-state event type. Debounce: Selectable for each channel. User-selectable (5.6μS, 50.4μS, 408.8μS, or 3.276mS).


Counter/timer configuration: Four 16-bit counters can be configured into two 32-bit counters. Counter input: Each counter has an INA, INB, and INC port. These TTL input signals control start/stop, reload, event input, external clock, trigger, and up/down operations. Counter output: Each counter has one output signal. The TTL output is used for waveform output, watchdog active indicator, or 1.6μS pulse upon counter function completion. Programmable as active high or low. Counter clock frequencies: Selectable for 20MHz, 10MHz, 5MHz, 2.5MHz, 1.25MHz or external up to 8MHz. Minimum I/P event: 100nS (debounce disabled). Minimum pulse measurement: 100nS (debounce disabled). Minimum period measurement: 200nS (debounce disabled). Minimum gate/trigger pulse: 100nS (debounce disabled).

CompactPCI bus Compliance

Meets PCI spec. V2.2 and PICMG 2.0, R3.0. Data transfer bus: Slave with 32-bit, 16-bit, and 8-bit data transfer operation. Interrupts (INTA#): Interrupts requested on Interrupt A. Plug-and-Play: The system maps the base address into the PCI bus 32-bit memory space.


Operating temperature: 0 to 70°C (AcPC424) or -40 to 85°C (AcPC424E). Storage temperature: -55 to 125°C. Relative humidity: 5 to 95% non-condensing. MTBF: Consult factory. Power: 216mA at 5V, typical.

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    AcPC424: Digital Input/Output Module Differential, TTL, Counter/Timer

    • 24 differential I/O, 16 TTL I/O
    • Four 16-bit counter/timer channels with six operating modes
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