The Allen‑Bradley 1747‑BSN, also cataloged as the 1747‑BSN backup scanner module, operates as a dedicated hardware component for redundant Remote I/O and DH+/DH‑485 communication within SLC 500 backplane networks.
The 1747‑BSN participates in deterministic backplane communication used across Allen‑Bradley SLC 500 architectures. Scanner redundancy relies on synchronized token‑passing intervals for DH+ and Remote I/O networks. I/O density scaling is maintained by mapping each BSN pair to identical network segments, preventing channel skew during switchover. Firmware flash compatibility resides entirely within the SLC processor; the BSN contains no user‑upgradeable firmware and provides fixed electrical behavior across controller revisions.
Frequently Asked Questions
Q: Can the 1747‑BSN be hot‑swapped? A: No. The module must be inserted or removed only 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 firmware updates? A: No. All configuration and firmware handling occur in the SLC processor; the BSN is hardware‑fixed.
Field Installation Guidelines
Install BSN modules in complementary pairs to maintain redundancy.
Ensure proper seating in the 1746 backplane to avoid bent pins or intermittent communication.
Route DH+, DH‑485, and Remote I/O cabling separately from high‑voltage conductors to reduce noise coupling.
Verify backplane power capacity when multiple communication modules coexist.
Maintain non‑condensing humidity conditions to prevent terminal oxidation.
Label network segments clearly to support maintenance and fault tracing.
