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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Compatible Processors | SLC 5/02, 5/03, 5/04, 5/05 |
| Backplane Current @ 5 V DC | 800 mA |
| RIO Baud Rates | 57.6 K, 115.2 K, 230.4 K |
| Max RIO Cable Distance | 3048 m (10,000 ft) at 57.6 K (Belden 9463) |
| High-Speed Serial Link (HSSL) | 2 Mbaud, max 4.5 m (15 ft) |
| Data Table Transfer Capacity | Up to 2 KWords per module pair |
| Local Serial Link (LSL) | Status exchange between modules in same chassis |
| Switchover Time | < 50 ms (plus one secondary program scan) |
| Operating Temperature | 0 °C to +60 °C |
| Storage Temperature | –40 °C to +85 °C |
| Humidity | 5–95 % non-condensing |
| Agency Approvals | UL, C-UL Class I Div 2 Groups A–D, CE |
4. Product Introduction
The Allen-Bradley 1747-BSN is a backup scanner module for SLC 500 systems that provides hot-standby redundancy for Remote I/O, Data Highway Plus, and RS-232 channels. One module sits in the primary chassis and its complementary unit sits in the secondary chassis.
The primary module controls the RIO network while the secondary monitors via the High-Speed Serial Link. On primary failure, control transfers in under 50 ms. The module also supports limited data-table synchronization (up to 2 KWords per pair) and optional Local Serial Link status sharing when multiple BSN modules share a chassis.
1747-BSN
1747-BSN
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Secondary processor shows RIO faults | HSSL cable fault or mismatched baud rate | ✅ High | Verify HSSL cable continuity and length ≤ 15 ft; match DIP settings | Replace cable or correct DIP switches |
| No switchover on primary fault | Incorrect module addressing or DIP config | ✅ High | Confirm module addresses and primary/secondary roles via DIP switches | Re-set DIP switches per manual; power-cycle both chassis |
| HSSL communication failure | Cable too long or damaged | ✅ High | Measure cable length; inspect connectors | Use only approved HSSL cable ≤ 4.5 m |
| RIO network intermittent | Termination resistor wrong or missing | ❌ Medium | Check end-of-line resistors match baud rate (82 Ω or 150 Ω) | Install correct terminating resistors |
| Data table values not synchronized | M0/M1 file sizes too small or not configured | ✅ High | Verify M0/M1 files ≥ 32 words (up to 5548) in RSLogix 500 | Adjust file sizes and re-download program |
| Module LED status abnormal | Backplane power or slot seating issue | ❌ Low | Measure 5 V backplane; reseat module | Check power supply capacity and module seating |
If diagnostics remain unclear, capture module status LEDs, DIP switch photos, and processor fault codes before contacting support.
6. Frequently Asked Questions (FAQ)
Q: Is the 1747-BSN still available new from Rockwell? No. The SLC 500 platform is discontinued. Units on the market are New Surplus or refurbished. Confirm stock and condition before ordering.
Q: Which processors work with the 1747-BSN? SLC 5/02, 5/03, 5/04, and 5/05 only. It will not function with SLC 5/01 or fixed-style controllers.
Q: Do I need two 1747-BSN modules? Yes. The system requires a complementary pair—one in the primary chassis and one in the secondary chassis. A single module cannot provide backup.
Q: Can the 1747-BSN be hot-swapped? No. Power down the chassis before removing or inserting the module. Hot-swapping risks backplane damage and loss of redundancy.
Q: How much data can be transferred over the HSSL? Each module pair can transfer up to 2 KWords of data-table information. Adding more BSN pairs in the same chassis increases total capacity (up to 16 KWords with eight pairs).
Q: What is the maximum RIO network distance? 3048 m (10,000 ft) at 57.6 Kbaud using Belden 9463 twinax with proper termination. Distance drops to 1524 m at 115.2 Kbaud and 762 m at 230.4 Kbaud.
Q: Why is New Surplus priced lower than original list? These are genuine Allen-Bradley modules from excess inventory or cancelled projects. They are unused and typically supplied with anti-static protection. They are not refurbished unless specifically stated.
