Digital input/output specifications

Terminals configurable for digital input and output (I/O) including status high/low, pulse width modulation, external interrupt, edge timing, switch closure pulse counting, high-frequency pulse counting, plus UART Universal Asynchronous Receiver/Transmitter for asynchronous serial communications., RS‑232 Recommended Standard 232. A loose standard defining how two computing devices can communicate with each other. The implementation of RS-232 in Campbell Scientific data loggers to computer communications is quite rigid, but transparent to most users. Features in the data logger that implement RS-232 communications with smart sensors are flexible., RS-422 Communications protocol similar to RS-485. Most RS-422 sensors will work with RS-485 protocol., RS‑485 Recommended Standard 485. A standard defining how two computing devices can communicate with each other., SDM Synchronous Device for Measurement. A processor-based peripheral device or sensor that communicates with the data logger via hardwire over a short distance using a protocol proprietary to Campbell Scientific., SDI‑12 Serial Data Interface at 1200 baud. Communications protocol for transferring data between the data logger and SDI-12 compatible smart sensors., I2C Inter-Integrated Circuit is a multi-controller, multi-peripheral, packet switched, single-ended, serial computer bus., and SPI Serial Peripheral Interface - a clocked synchronous interface, used for short distance communications, generally between embedded devices. serial-communications functions. Terminals are configurable in pairs for 5 V or 3.3 V logic for some functions.

NOTE:

Conflicts can occur when a control port pair is used for different instructions (TimerInput(), PulseCount(), SDI12Recorder(), WaitDigTrig()). For example, if C1 is used for SDI12Recorder(), C2 cannot be used for TimerInput(), PulseCount(), or WaitDigTrig().

Terminals: C1-C8

Sustained Logic Input Voltage without Damage: ±20 VDC

Logic Levels and Drive Current:

Terminal pair configuration	5 V source	3.3 V source
Logic low	≤ 1.5 V	≤ 0.8 V
Logic high	≥ 3.5 V	≥ 2.5 V

Switch closure input

Terminals: C1-C8

Pull-Down Resistance: Configurable in terminal pairs with 100 kΩ

Pull-Up Resistance: Configurable in terminal pairs with 100 kΩ (weak) or 2.2 kΩ (strong)

Maximum Input Frequency: 250 Hz

Minimum Switch Closed Time: 1 ms

Minimum Switch Open Time: 1 ms

Maximum Bounce Time: 1 ms open without being counted

Software Debounce Time: 1 ms

High-frequency input

Terminals: C1-C8

Pull-Down Resistance: Configurable in terminal pairs with 100 kΩ

Pull-Up Resistance: Configurable in terminal pairs with 100 kΩ (weak) or 2.2 kΩ (strong)

Maximum Input Frequency: 1 MHz

Edge timing

Terminals: C1-C8

Maximum Input Frequency: 1 MHz

Resolution: 20 ns

Edge counting

Terminals: C1-C8

Maximum Input Frequency: 1 MHz

Quadrature input

Terminals: C1-C8 can be configured as digital pairs to monitor the two sensing channels of an encoder.

Maximum Frequency: 500 kHz

Resolution: 20 ns or 50 MHz

Minimum Pulse Width: 10 µs

Pulse-width modulation

Terminals: C1-C8

Modulation Voltage: Logic high

Maximum Period: 43 seconds

Resolution: 10 ns

Maximum time between counter or timer instructions

86 seconds