SIEMENS 6ES7321-1BH02-0AA0 — 16-Channel 24VDC Digital Input Module | SIMATIC S7-300 SM 321
Engineering Background
The SIMATIC S7-300 series has been the backbone of discrete and process automation for over three decades. The SM 321 digital input sub-family provides the field-signal acquisition layer for S7-300 CPUs, converting real-world 24 VDC sensor signals into the binary data processed by the PLC program. The 6ES7321-1BH02-0AA0 is the 16-channel, 24 VDC variant — the most widely deployed SM 321 module across automotive, food & beverage, water treatment, and general manufacturing sectors.
Product Positioning
Designed for procurement engineers who require a drop-in replacement or capacity expansion for existing S7-300 racks, this module offers full backward compatibility with all S7-300 CPUs and STEP 7 / TIA Portal V13+ engineering environments. Konmask supplies this module as a genuine SIEMENS component, sourced through verified industrial channels, with full traceability documentation available on request.
Complete Technical Specifications
| Order Number | 6ES7321-1BH02-0AA0 |
| Module Family | SM 321 — Digital Input Module |
| Platform | SIMATIC S7-300 |
| Number of Inputs | 16 × DI (2 × 8-channel groups) |
| Input Voltage (Rated) | 24 VDC |
| Input Voltage Range | 20.4 – 28.8 VDC (SELV/PELV) |
| Signal 1 (High) Level | 13 – 30 VDC |
| Signal 0 (Low) Level | -3 – +5 VDC |
| Input Current (Typ.) | 7 mA at 24 VDC |
| Input Delay | 1.2 / 6.4 ms (configurable) |
| Galvanic Isolation | Yes — between channels and backplane bus (group isolation) |
| Isolation Groups | 2 groups of 8 channels each |
| Backplane Bus Current Draw | Max. 50 mA (5 VDC) |
| Power Dissipation | Max. 4.5 W |
| Connector Type | 40-pin front connector (not included) |
| Dimensions (W × H × D) | 40 × 125 × 120 mm |
| Weight | Approx. 200 g |
| Operating Temperature | 0 – 60 °C (horizontal), 0 – 40 °C (vertical) |
| Storage Temperature | -40 – +70 °C |
| Relative Humidity | 10 – 95 % (non-condensing) |
| Degree of Protection | IP 20 |
| CE / UL / cULus | Yes |
| HS Code | 8537.10 |
| Country of Origin | Germany |
Proven Application Environments
- Automotive Assembly Lines — High-density sensor acquisition for body-in-white and powertrain stations
- Water & Wastewater Treatment — Pump status, valve position, and level switch monitoring
- Food & Beverage Processing — Hygienic-area sensor interfacing with 24 VDC proximity switches
- Pharmaceutical Manufacturing — GMP-compliant discrete I/O for batch process control
- Building Automation & HVAC — Fan status, damper feedback, and alarm input aggregation
- Machine Tool & Packaging — High-speed input capture for servo-driven indexing machines
- Energy & Utilities — Substation auxiliary contact monitoring and protection relay interfacing
Engineering Advantages
- Galvanic Isolation — Two isolated 8-channel groups protect the CPU backplane from field-side transients and ground loops
- Configurable Input Delay — 1.2 ms or 6.4 ms selectable per group via STEP 7 / TIA Portal HW Config, enabling noise immunity tuning without hardware changes
- Hot-Swap Compatible — Module can be replaced under power in S7-300 racks equipped with active bus connectors (with appropriate CPU configuration)
- Diagnostic Capability — Supports group error LED indication; integrates with S7-300 diagnostic buffer for fault tracing
- Wide Thermal Range — Rated to 60 °C horizontal mounting, suitable for non-air-conditioned control cabinets in harsh industrial environments
- IEC 61131-2 Compliant Inputs — Type 1 / Type 3 input characteristics ensure compatibility with standard 24 VDC sensors and switches
System Architecture & Signal Flow
The 6ES7321-1BH02-0AA0 occupies one slot in the S7-300 rack and communicates with the CPU via the S7-300 backplane bus (P-bus). Field wiring connects to the 40-pin front connector (order separately: 6ES7392-1AJ00-0AA0 or equivalent). Signal flow is as follows:
- Field sensor energizes input terminal (24 VDC)
- Optocoupler isolates field voltage from logic side
- Input filter (1.2 or 6.4 ms) debounces signal
- Logic state written to process image input (PII) table each CPU scan cycle
- CPU program reads PII via standard IEC 61131-3 instructions (e.g.,
%I0.0addressing)
Slot addressing follows standard S7-300 rules: module address is determined by physical slot position (Slot 4 = byte 0, Slot 5 = byte 2, etc.), configured automatically in STEP 7 / TIA Portal HW Config.
Sourcing & Quality Verification
- Genuine SIEMENS Components — All units sourced through verified industrial distribution channels; counterfeit-free guarantee
- Functional Test — Each module undergoes power-on and I/O channel verification prior to dispatch
- Traceability — Batch records and supplier documentation available on request for regulated industries
- Packaging — Ships in original or equivalent ESD-safe packaging with protective foam insert
- Warranty — 12-month Konmask warranty covering manufacturing defects and functional failure
Procurement Process
- Confirm Quantity & Lead Time — Contact us via the form below or email support@konmask.com with your required quantity and delivery deadline
- Receive Quotation — We respond within 1 business day with pricing, availability, and estimated shipping timeline
- Place Order — Checkout directly on Konmask.com or via purchase order (PO) for approved B2B accounts
- Dispatch & Tracking — Orders ship within 1–3 business days; tracking number provided via email
- Delivery & Acceptance — Inspect on arrival; report any discrepancies within 48 hours for immediate resolution
For bulk orders (>10 units), OEM projects, or system integrator pricing, please contact our technical sales team directly.
Technical FAQ
Q: Is this module compatible with S7-300 CPUs using TIA Portal?
A: Yes. The 6ES7321-1BH02-0AA0 is fully supported in TIA Portal V13 and later. Select the module from the hardware catalog under SIMATIC S7-300 → SM 321.
Q: Can I use this module with an ET 200M distributed I/O station?
A: Yes. The SM 321 family is compatible with the IM 153-x interface modules used in ET 200M stations, enabling distributed deployment over PROFIBUS DP.
Q: What front connector do I need?
A: The standard 40-pin screw-type front connector is 6ES7392-1AJ00-0AA0. Spring-type alternative: 6ES7392-1BJ00-0AA0. These are sold separately.
Q: What is the difference between 6ES7321-1BH02-0AA0 and 6ES7321-1BH50-0AA0?
A: The -1BH50 variant adds individual channel diagnostics and interrupt capability. The -1BH02 is the standard version without hardware interrupt support — suitable for the majority of applications.
Q: Can I replace a -1BH01 with a -1BH02?
A: Yes, the -1BH02 is the successor to the -1BH01 and is a direct drop-in replacement with identical electrical and mechanical characteristics.
Q: Do you provide a certificate of conformity?
A: Yes, upon request. Please specify your requirement at the time of order.
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