CM2
8-Ch. ARINC 429/575 Communications Interface and 12-Ch. Discrete I/O Function Module
The CM2 is a high-performance NAI smart Configurable Open Systems Architecture™ (COSA®) function module that integrates two critical field-proven I/O functions into a single module: ARINC 429/575 communications and Discrete I/O. Built on NAI’s modular and scalable COSA architecture, the CM2 combines the functionality of the AR1 (ARINC 429/575) and DT4 (Discrete I/O) smart modules, delivering efficient, high-density integration for aerospace and defense systems requiring avionics data interfacing and discrete signal control.
1) ARINC 429/575 Interface: 8 channels, fully programmable for Transmit or Receive (based on AR1)
2) Discrete I/O Interface: 12 channels, fully programmable as input or output (based on DT4)
ARINC 429/575 Communications Interface (AR1-type)
The CM2 ARINC 429/575 communication section, based on NAI’s AR1 smart function module, provides 8 fully programmable channels, each configurable for either transmit (Tx) or receive (Rx) operation. All channels support both ARINC 429 and ARINC 575 protocols, with selectable data rates and programmable parity control for flexible avionics integration.
Discrete I/O (DT4-type)
The CM2 Discrete I/O section, based on NAI’s DT4 smart function module (the enhanced version) features 12 programmable channels for either input (voltage or contact sensing with programmable, on-module pull-up/pull down current sources), or output (current source, sink, or push-pull) up to 500 mA per channel from an applied, external 5 – 60 VCC source. These modules can sense broken input connections and whether an input is shorted to +VCC or to ground. Additional enhanced features are listed below
- ARINC 429/575 Characteristics: see below
- Input/Output Format: Eight channels, programmed for either Rx or Tx per channel
- Frequency: 100 kHz or 12.5 kHz operation (programmable)
- Buffers: 255 message FIFO Rx or Tx FIFO buffering or scheduled transmits; SDI/Label Filtering
- Built-In-Test: Loopback test
- Format: AR429 or 575 programmable/channel; ARINC 429 reserves bit 32 for parity, while ARINC 575 can use bit 32 for either parity (when BNR) or data (when BCD).
- Signal Levels Specifications (ARINC 429 & ARINC 575): see below
- Mode of Operation: Differential (ARINC 429); Differential (ARINC 575)
- Data Rate: 100 kHz (ARINC 429); 12.5 kHz (ARINC 575)
- Driver Output Signal Level (Min Loaded): ±10.0 V (ARINC 429); ±10.0 V (ARINC 575)
- Receiver Input Voltage Range: -17 V to +17 V (ARINC 429); -17 V to +17 V (ARINC 575)
- Receiver Input Resistance (Ohms): 15 K (ARINC 429); 15 K (ARINC 575)
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- Discrete I/O Characteristics: see below
- Input Range: 0 to 60 VDC. Programmable for either voltage or switch closure sensing
- Overvoltage Surge Protection: 80 VDC max. (< 50 ms); 100 VDC max. (< 1 μs)
- Voltage/Contact Sensing: Software selectable per channel/bank. When the input channel is utilized for direct voltage sense, Vcc is not required. When input is used to detect switch closures, Vcc is required to provide a current source (pull-up). Vcc per channel bank must be between 5 VDC min. and 60 VDC max. This module has 2 Vcc banks, each with 6 channels for a total of 12 channels/module.
- Input Pulse Detection: A pulse of greater than 20 μs minimum width will be sensed and reported by the appropriate High–Low or Low-High transition status/interrupt.
- Input Impedance: 1 MΩ (with or without power applied to module).
- Switching Threshold: Four levels (High, Low, Short to +V, Short to ground) are programmable from 0 to 60 VDC with 10-bit resolution.
- Voltage Measurement: User can read input voltage of each channel. From: LSB=100 mV; Accuracy: ±3 LSB’s (300 mV) over temp. to: 1% FSR
- HIGH/LOW Differential (Hysteresis): 300 mV min. recommended. Programmable by using Upper & Lower thresholds.
- Debounce: Programmable per channel from 0x00000000 (deactivated) to 0xFFFFFFFF (2^32 * 10μs) LSB= 10 μs; 32-bit resolution.
- Update Rate: Each channel is updated every 10 μs.
- Additional Enhanced Input Mode Operation: Pulse Measurements, Transition Timestamps, Transition Counters, Period Measurement and Frequency Measurement.
- Output Formats: Low-Side (current sink), High-Side (current source) or Push-Pull (current source-sink); programmable per channel.
- Output Voltage Range: 0 to 60 VDC (Output voltage is defined by the user provided Vcc applied to channel bank). Low-side drive does not require Vcc. High-side and push-pull drive requires Vcc.
- Overvoltage Surge Protection: 80 VDC max. (< 50 ms); 100 VDC max. (< 1 μs)
- Output Current: 0.5 A maximum (28 V Vcc typical) per channel; 2 A total per Vcc bank (total Module capacity 4 A); Measurement accuracy: ±10% ± 25 mA
- Output Impedance: < 1 Ω (0.5 Ω typical)
- Current Share Applications: 0.5 A maximum (28 V Vcc typical) per channel. 2 A total per Vcc bank (total Module capacity 4 A). Each channel can be programmed to generate frequency, pulse or arbitrary pulse width with 10 microsecond minimum resolution. Short circuit protected.
- Overcurrent Protection: Low current (average): > 625 mA average over 3 ms; High current (pulse): > 6 amps for less than or equal to 30 μs
- Additional Enhanced Output Mode Operation: PWM Output and Pattern Generator Output.
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- General Characteristics: see below
- Power*: 5 VDC @ 220 mA / ±12 VDC @ 60 mA
- Weight: 1.75 oz. (50 g)
- *: Pending design verifications and qualification.
7/16/2025 8:02:39 AM
NAI’s Configurable Open Systems Architecture™ (COSA®) offers a choice of over 100 smart I/O, communication, and Ethernet switch functions, providing the highest package density and greatest flexibility of any multifunction I/O board in the industry. Preexisting, fully-tested functions can be combined quickly and easily in an unlimited number of ways. Choose the ideal platform for your application below. Each I/O function has dedicated processing, unburdening the system Single Board Computer (SBC) from unnecessary data management overhead.
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