1747-BSN | Allen-Bradley | Backup Scanner Module

Allen‑Bradley 1747‑BSN Backup Scanner Module

The Allen‑Bradley 1747‑BSN, also cataloged as the 1747‑BSN backup scanner module, serves as the primary hardware component used to execute redundant Remote I/O and DH+/DH‑485 communication across SLC 500 platforms. The module interfaces directly with the 1746 backplane to maintain complementary scanner operation and communication continuity.

Hardware Specifications

Backplane Bus Communication Velocity and I/O Density Scaling

Within SLC 500 architectures, the 1747‑BSN participates in deterministic backplane bus arbitration, ensuring that redundant scanner pairs maintain synchronized communication cycles. The module’s 800 mA load at 5 V influences overall I/O density scaling, requiring proper power‑budget allocation when multiple communication modules coexist. DH+ and Remote I/O networks operate with fixed token‑passing intervals, and the BSN pair preserves these intervals during switchover events. Firmware flash compatibility is determined by the installed SLC processor; the BSN itself contains no user‑upgradeable firmware.

Frequently Asked Questions

Q: Can the 1747‑BSN be hot‑swapped in a powered SLC chassis A: No. The module should only be inserted or removed when the chassis is de‑energized to avoid backplane communication faults.

Q: How many networks can a BSN pair back up A: One Remote I/O or DH+ network and one RS‑232/DH‑485 communication channel per complementary BSN module pair.

Q: Does the BSN require configuration firmware updates A: No. All configuration is handled by the SLC processor; the BSN contains no user‑upgradeable firmware.

Field Installation Guidelines

Maintain proper seating of the module to avoid bent backplane pins. Ensure that DH+, DH‑485, or Remote I/O cabling is routed separately from high‑voltage conductors to reduce noise coupling. Verify that complementary BSN modules are installed in the correct chassis slots to maintain redundancy. Confirm backplane power capacity when multiple communication modules are present. Keep humidity within non‑condensing limits to prevent terminal oxidation.