Siemens 6ES7321-1CH00-0AA0 – SM 321 Digital Input Module | SIMATIC S7-300 Platform
The Siemens 6ES7321-1CH00-0AA0 is a Signal Module (SM 321) designed for the SIMATIC S7-300 programmable logic controller platform. Engineered for industrial-grade discrete signal acquisition, this module provides 8 digital inputs rated at 24 VDC, delivering reliable process data to the CPU in demanding manufacturing and process automation environments. At Konmask.com, every unit is sourced through verified supply channels and undergoes multi-point inspection before dispatch.
Product Positioning: Ideal for procurement engineers and system integrators who require a drop-in replacement or expansion module for existing S7-300 installations. The 6ES7321-1CH00-0AA0 is a cost-effective, field-proven solution for discrete I/O expansion without the need for additional interface hardware.
Complete Technical Specifications
- Part Number: 6ES7321-1CH00-0AA0
- Module Type: SM 321 — Digital Input Module
- Platform: SIMATIC S7-300
- Number of Inputs: 8 DI
- Input Voltage: 24 VDC
- Input Current (typical): 7 mA per channel
- Isolation: Optocoupler isolation between field and backplane bus
- Signal Delay: Configurable (0.1 ms – 20 ms)
- Backplane Bus Interface: S7-300 standard backplane connector
- Dimensions (W × H × D): 40 × 125 × 120 mm
- Weight: Approx. 260 g
- Operating Temperature: 0 °C to +60 °C
- Storage Temperature: −40 °C to +70 °C
- Degree of Protection: IP 20
- Certifications: CE, UL, cULus, ATEX (Zone 2)
- Country of Origin: Germany
- MLFB / Order Number: 6ES7321-1CH00-0AA0
Proven Application Environments
- Discrete manufacturing lines — machine tool control, conveyor interlocking, press safety circuits
- Process industries — chemical plant valve position feedback, pump status monitoring
- Building automation — HVAC damper position, fire-door status, access control integration
- Water & wastewater — level switch inputs, pump run/fault signals
- Energy & utilities — substation auxiliary contact monitoring, generator status
- Food & beverage — CIP cycle monitoring, filling line sensor inputs
Engineering Advantages
- Plug-and-Play Compatibility: Direct replacement for existing S7-300 SM 321 slots — no hardware modification required.
- Optocoupler Isolation: Protects the CPU backplane from field-side voltage transients and ground loops.
- Configurable Input Delay: Software-selectable filter times via STEP 7 / TIA Portal to suppress contact bounce and EMI noise.
- Compact Form Factor: 40 mm wide single-slot module minimises rack space consumption.
- Wide Operating Temperature: Rated to 60 °C continuous — suitable for non-air-conditioned panel environments.
- Diagnostic Capability: Supports hardware interrupt and diagnostic interrupt for rapid fault detection.
System Architecture & Signal Flow
Field-side sensors or switches connect to the 20-pin front connector of the 6ES7321-1CH00-0AA0. Each input channel passes through an optocoupler stage that electrically isolates the 24 VDC field circuit from the S7-300 backplane bus. The module communicates with the CPU via the standard S7-300 backplane, transferring 8-bit input image data each scan cycle. Configuration — including input delay time and diagnostic interrupt enable — is performed in STEP 7 HW Config or TIA Portal Device Configuration without any physical DIP switches.
Sourcing & Quality Verification
Konmask.com operates a 4-step verification process for every Siemens module:
- Supplier Audit: All supply partners are evaluated against Siemens authorised distributor records and ISO 9001 quality management documentation.
- Physical Inspection: Label authenticity, hologram integrity, housing mould quality, and connector pin condition are checked on receipt.
- Functional Bench Test: Modules are powered and input channels are exercised with a calibrated 24 VDC source to verify correct LED indication and backplane communication.
- Packaging & Documentation: Units are repackaged in anti-static ESD bags with original or equivalent documentation and shipped with a Konmask inspection certificate.
Procurement Process
- Confirm your required quantity and delivery timeline via support@konmask.com or the on-site enquiry form.
- Receive a formal quotation with lead time, unit price, and shipping options within 24 business hours.
- Issue a Purchase Order or proceed with online checkout.
- Receive tracking information and Konmask inspection certificate upon dispatch.
- Post-delivery technical support available via email or WhatsApp.
Technical FAQ
Q: Is the 6ES7321-1CH00-0AA0 compatible with S7-300 CPUs such as the 315-2DP or 317-2DP?
A: Yes. The SM 321 modules are compatible with all standard S7-300 CPUs. Slot assignment is configured in STEP 7 or TIA Portal HW Config.
Q: Can this module be used in an ET 200M distributed I/O rack?
A: Yes. The 6ES7321-1CH00-0AA0 is fully compatible with the ET 200M IM 153-x interface module when used in a distributed configuration over PROFIBUS DP or PROFINET.
Q: What is the maximum cable length for field wiring?
A: Siemens specifies a maximum of 600 m for unshielded cable and 1000 m for shielded cable at 24 VDC input voltage.
Q: Do you supply original Siemens packaging?
A: Where available, units are supplied in original Siemens packaging. Refurbished or surplus stock is clearly labelled and supplied in Konmask-branded ESD packaging with full inspection documentation.
Q: Can I request a Certificate of Conformance (CoC)?
A: Yes. A Konmask CoC is included with every shipment. Siemens factory CoC can be requested for new-in-box stock subject to availability.
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