D3J0128 Modbus
28-channel fully isolated Modbus-RTU/RS-485 digital input module for high-density centralized signal acquisition.
🔍 Click to enlarge · 1/3Technical Specifications
| Protocol | MODBUS-RTU over half-duplex RS-485 (differential A/B twisted pair); additional MODBUS-ASCII and AT commands; optional 2.4GHz wireless MODBUS-OTA |
|---|---|
| I/O Configuration | 28 fully isolated digital inputs (pure input, no relay/transistor output); plus 2 analog input channels and 1 x 5V/100mA sensor supply output |
| Product Identification Code | 0x3128 (default slave address 0x02) |
| Supply Voltage | DC 11-28V |
| Supply Current | <1500mA |
| Power Supply Ripple | <1Vp-p |
| Default Communication Settings | 9600bps, 8 data bits, even parity, 1 stop bit, slave address 0x02 |
| USB Mode Address | Fixed at 0x01 when connected over USB; RS-485 port then switches to master mode |
| Configurable Baud Rate | 300 / 600 / 1200 / 1800 / 2400 / 4800 / 7200 / 9600 / 14400 / 19200 / 28800 / 38400 / 56000 / 57600 / 76800 / 115200 bps |
| Configurable Parity | None / Odd / Even (default Even) |
| Configurable Stop Bits | 1 (default) / 1.5 / 2 |
| Slave Address Range | 1-247 (0x01-0xF7) |
| Supported Function Codes | 0x02 Read Discrete Inputs, 0x04 Read Input Registers, 0x03 Read Holding Registers, 0x06 Write Single Holding Register, 0x10 Write Multiple Holding Registers, 0x16 Mask Write Register, 0x17 Read/Write Multiple Holding Registers, 0x11 Report Server ID |
| Exception Codes | 0x01 ENOFUNC (unsupported function code), 0x02 ENOADR (address/quantity out of range), 0x03 EINVAL (invalid length/field), 0x04 EDEVICE (execution error, e.g. writing an illegal value) |
| Digital Input Threshold | About 3V (above = high level, below = low level) |
| Input Edge Counting | Per-channel DINnCNT register, increments on rising edge; pulse frequency up to 5Hz; rolls over at 65535; can be cleared by writing a value |
| Input Filtering | Per-channel DINnFLT register, 1-65535ms adjustable (0 = off); savable through power loss by writing MODESAVE = "MS" |
| Automatic Reporting | Supports active reporting on interval or on input change (AT format, over USB or RS-485); disabled by default |
| Register Protection | Sensitive registers (NAME, SRLCFG, wireless config, etc.) require writing ASCII "UL" (0x554C) to SAFELCK (0x000E) to unlock; SAFELCK auto re-locks after each write, or if a bus command for another device, a parity error, or a CRC error is detected |
| Communication Port Stress | DC 0-5V (normal); DC 50V (absolute maximum) |
| Input Stress | DC 0-30V (normal); DC 50V (absolute maximum) |
| Communication Isolation Voltage | <250V (normal); DC 1000V, 60s (type test only) |
| Input Isolation Voltage | <250V (normal); DC 1000V, 60s (type test only) |
| One-Time Fuse | DC 250V, 3000mA, slow-blow |
| Operating Temperature | -20 ~ 60C |
| Storage Temperature | -40 ~ 85C |
| Module Dimensions | 158 x 88 x 59mm (tolerance +/-5%), 5.08mm terminal pitch |
| ESD Immunity (IEC61000-4-2) | 4kV on all terminals: normal operation (A) |
| EFT Immunity (IEC61000-4-4) | 2kV/5kHz/2min: normal operation (A); 4kV/5kHz/2min: no permanent damage (C) |
| Surge Immunity (IEC61000-4-5) | 1kV on all terminals to ground: no permanent damage (C) |
| Creepage Distance | Pollution degree 3, material group IIIa/IIIb, required >6mm, measured >6.5mm (IEC60950-2L/2N) |
| Clearance | Pollution degree 3, required >2mm, measured >2.2mm (IEC60950-2H) |
| Response Time | Input response typically 20ms; serial command reply time up to 25ms |
Overview
D3J0128 is a medium-power MODBUS-RTU / RS-485 digital input module built around a dedicated ASIC. It provides 28 fully isolated digital inputs that a PLC, HMI, or SCADA system reads over a standard RS-485 bus, giving panel builders and system integrators a way to bring dozens of switch, sensor, or status signals into a single Modbus node instead of many small modules. It is a pure-input product: it has no relay or transistor outputs, and any output-related registers or software functions do not apply to it.
Supply voltage is DC 11-28V, and the default communication settings are 9600 baud, 8 data bits, even parity, 1 stop bit, with default slave address 0x02 (0x01 when connected over USB). Each of the 28 inputs has its own edge counter (rising edge, pulse frequency up to 5Hz, rolling over at 65535) and adjustable digital filter (1-65535ms, power-loss safe), and the module also includes 2 analog input channels and 1 x 5V/100mA sensor supply output in addition to the 28 digital inputs. EFT immunity is rated at 2kV, above the 1kV requirement of IEC61000-6-2-2016 for industrial environments.
Features & Benefits
28 channels, one bus node, one poll
A single D3J0128 covers what would otherwise take seven 4-channel modules. All 28 discrete inputs live in one register block from 0x0000 under one slave address, so a single Modbus function code 0x02 request returns the whole cabinet in one answer -- replied within 25ms. Fewer nodes means less polling overhead, fewer tags to configure in the SCADA, and a shorter, simpler RS-485 trunk.
Per-channel hardware debounce that survives power loss
Every one of the 28 channels has its own DINnFLT filter register, adjustable from 1 to 65535ms (0 = off), so a bouncing relay contact on channel 3 can be filtered at 20ms while a fast limit switch on channel 12 stays at 1ms. Write MODESAVE = "MS" and the settings survive a power cut. That removes 28 debounce timers from the PLC ladder and stops chattering contacts from flooding the alarm list.
Every channel counts its own edges -- no pulses lost between polls
Each input carries a DINnCNT rising-edge counter (up to 5Hz, rolling over at 65535, clearable by writing a value). The module keeps counting cycles, strokes, or trip events in hardware even when the master polls once a second, so you get true totals instead of whatever the poll happened to catch -- without a single line of counting logic upstream.
Fully isolated inputs, EFT immunity at double the industrial requirement
Every digital input and the RS-485 port are electrically isolated from the internal logic (isolation voltage under 250V in service, type tested at DC 1000V for 60 seconds), so 28 field wires running beside contactor coils and VFD cables cannot drag ground loops into your readings. EFT is rated 2kV/5kHz for 2 minutes with normal operation (A) -- twice the 1kV that IEC61000-6-2-2016 asks of industrial equipment -- and 4kV causes no permanent damage (C); ESD is 4kV (A) and surge 1kV to ground (C). For sites with frequent inductive switching, the input-reinforced "XS" order suffix hardens the input stage further.
Built to survive wiring mistakes
The supply is protected against reverse polarity, over-current, surge, and automotive load dump, and is backed by a DC 250V / 3000mA slow-blow fuse; the input and communication ports are also reverse-polarity and surge protected. Inputs work over DC 0-30V and tolerate 50V as an absolute maximum, so a wire landed on the wrong 24V rail during commissioning does not end in a scrapped board.
Details that show up on the PCB, not just the datasheet
Creepage on the high-voltage side is slotted to a measured >6.5mm where pollution degree 3 with material group IIIa/IIIb requires >6mm, and clearance measures >2.2mm against a >2mm requirement (IEC60950). A green power LED plus 28 yellow per-channel LEDs let an electrician verify every field wire by eye, at the terminal, before any host software exists.
Free USB port doubles as the commissioning tool
Besides RS-485 the module has a USB port: plug in a laptop and the module answers at fixed address 0x01 while the RS-485 side switches to master mode, so it also works as a USB-to-serial converter for the rest of the bus. MODBUS-ASCII suits HMIs and touch panels, plain-text AT commands get a quick test running in minutes, and PC software is supplied -- you can prove the wiring before the PLC arrives.
Wide supply, bonus analog, optional wireless
DC 11-28V covers both 12V and 24V panels, and the module runs from -20 to 60C. Each board also throws in 2 analog inputs (1mV per bit, about 10-bit, typically 3% accuracy) and a 5V/100mA sensor supply for a free small measurement, and where cabling is impractical the 2.4GHz wireless MODBUS-OTA version (order option M2) replaces the trunk entirely.
Applications
Models & Ordering Information
D3J0128 Series
How to Select
- Choose the 28-channel D3J0128 when signal points are highly concentrated and approach or exceed twenty channels -- one board gives the lowest per-channel cost, fewest bus nodes, and least polling/configuration overhead.
- For points scattered across multiple locations, do not force them onto one 28-channel module; use the 4-channel D3J0104 or 8-channel D3J0108 for distributed, closer-to-the-signal deployment instead.
- For moderate concentration (roughly a dozen or so points), choose the 16-channel D3J0116.
- Where wiring is inconvenient, order the optional 2.4GHz wireless version instead of running an RS-485 bus.
- For sites with frequent strong EFT or inductive-load switching, order the input-reinforced version (order-code suffix "XS").
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When NOT to specify the D3J0128 — and what to use instead
The application needs to switch something - a contactor, indicator, valve, or pump - not just report a signal.
Why not: D3J0128's own spec lists its outputs as 'None - pure input module, no relay or transistor output'; there is no output register, relay, or transistor stage on the board at all.
Use instead: D3J0312 (12 isolated inputs + 8 outputs) for combined input+output on one board, or D3J0214 (14-channel output) if only outputs are needed.
Only a few signals (roughly 2-8) exist at one point, or the signals are spread across several separate locations rather than concentrated in one cabinet.
Why not: D3J0128's spec fixes it at '28 fully isolated digital inputs' on a 158mm board built for high-density, centralized acquisition - putting a handful of scattered signals on it leaves most of its 28 channels empty while still requiring the largest board footprint and full-length field wiring back to one node.
Use instead: D3J0104 (4 inputs), D3J0108 (8 inputs), or D3J0116 (16 inputs), sized to the actual point count and placed closer to each signal group.
The signal is part of a machine safety function - an emergency-stop circuit, a safety door interlock, a light-curtain OSSD, or a two-hand control input.
Why not: D3J0128 carries no Type/SIL/PL rating anywhere in its specification. Its digital inputs trip at an ordinary ~3V threshold and are only rated for normal DC 0-30V terminal stress and <250V basic isolation (type-tested to DC 1000V/60s) - nothing qualifies any input as an OSSD or a safety-rated channel, and the module has no dual-channel safety logic or forced-guided contact monitoring.
Use instead: DA31 Emergency-Stop Safety Relay Module (Cat.4/PL e/SIL 3) or DQSRN Safety Relay Module (DIP-switch selectable E-stop/OSSD/door-interlock/two-hand, Cat.4/PL e/SIL 3).
The host system communicates over Ethernet/EtherCAT, PROFIBUS, CANopen, or another fieldbus rather than serial Modbus.
Why not: D3J0128's only communication paths are RS-485 running Modbus-RTU (default 9600bps, 8 data bits, even parity, 1 stop bit), plus Modbus-ASCII, AT commands, a USB port, and an optional 2.4GHz wireless Modbus-OTA link - no other fieldbus stack is listed in its specification.
Use instead: No module in the D3J01/D3J02/D3J03/D4G0206 lineup speaks anything but Modbus-RTU/ASCII; pair the module with a separate Modbus-to-fieldbus gateway if the host requires a different protocol.
The signals need to drive a local action by themselves, without a PLC or SCADA host doing the polling and decision-making.
Why not: D3J0128 only exposes its input states to whatever master polls it over Modbus-RTU (or, if enabled, pushes them via interval/change-triggered auto-reporting) - it has no ladder logic, no local decision engine, and no output of any kind to act on a decision.
Use instead: D4G0206 Relay Module, a graphical schematic-programmed micro-PLC with 6 inputs and 4 relay/transistor outputs that runs its own logic without a host.
Specifications we do not publish yet
We only publish a figure once we are confident it is true. The items below are still being validated through further testing and real-world customer feedback, so for now we would rather leave them open than guess. If one of them matters to your design, ask us for the latest validated status.
- Ingress protection (IP) rating for the D3J0128 enclosure is not stated in the source specification.
- MTBF or expected service life for D3J0128 is not stated in the source specification.
- Terminal wire gauge (AWG/mm²) accepted by D3J0128's 5.08mm-pitch screw terminals is not stated in the source specification.
- Per-channel input current draw for D3J0128 is not stated - only total supply current (<1500mA) is given in the source specification.
- Maximum number of RS-485 nodes per bus segment and maximum cable length for D3J0128 are not stated in the source specification.
- A radiated/conducted EMC emission standard for D3J0128 is not stated - the source specification only lists ESD/EFT/surge immunity test levels.
- Module weight for D3J0128 is not stated - only the 158 x 88 x 59mm dimensions are given in the source specification.
Frequently Asked Questions
What is the D3J0128 used for?
Does the D3J0128 have any relay or transistor outputs?
What communication interfaces does it support?
Can all 28 input channels be read in a single Modbus request?
What extra features does D3J0128 include besides digital inputs?
How do I protect the configuration registers from accidental changes?
What supply voltage and communication defaults does D3J0128 use?
Can you provide certification documents for D3J0128?
Works Well Together
On the same machine or line, D3J0128 is typically ordered together with: Proximity Sensors · Photoelectric Sensors · Laser Distance Sensors
D6.5 Series Inductive Proximity Sensors (Ultra-Short 18mm / Y-Type / 35mm / 45mm)
6.5mm-diameter inductive proximity sensors for tight-clearance mounting where M8 sensors won't fit.
BGS-CX441 / BGS-CX442 Background Suppression Photoelectric Sensor
Wire-adjustable BGS sensor with 2 mm or 15 mm spot, 10-300 mm range, published black/white differential distance.
DDA-Y & DDB-Y Industrial Laser Distance Sensor (Phase-Shift)
Phase-shift laser distance sensors: 0.2-100 m range, millimeter accuracy, RS485 Modbus RTU, switching or analog output.
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