Description
What the 7AC020.9 Actually Is
The 7AC020.9 is one of B&R’s System 2003 rack accessories — a simple cover plate that snaps onto an unused slot on the local bus of a System 2003 module rack. Its job is purely mechanical and protective: it shields the exposed bus connector and slot opening from dust, debris, and accidental contact, and it helps maintain the rack’s EMC and airflow characteristics when not every position is populated by a CPU, I/O, or interface module.
It sits in the “7AC” accessory family alongside:
| Part number | Description |
|---|---|
| 7AC010.9 | System 2003 bus cover — 5-piece pack |
| 7AC020.9 | System 2003 bus cover — 1-piece pack |
| 7AC570.1 | System 2003 aPCI socket cover |
| 7AC911.9 | System 2003 bus connector |
There is no processor, memory, power terminal, or communication transceiver on this part — it contains no electronics at all.
How the “CANbus Controller” Mislabeling Happens
The inaccurate description on sites such as Xiongba (dcs-plc-module.com), Qilin Industry (aaadcs.com), and similar industrial-spare-part marketplaces appears to be keyword-stuffed boilerplate: the “200 MHz / 128 MB / 256 MB / 2× CAN / 12–48 VDC” block is copied into dozens of unrelated listings, and the words “B&R Automation” and “CANbus controller” are attached to whatever part number is being sold to improve search visibility. The giveaway is that the same specification block appears on multiple, physically unrelated B&R part numbers on those sites.
A useful rule of thumb when reading B&R part numbers: the 7AC prefix is reserved for System 2003 accessories (covers, connectors), while real CAN-capable System 2003 controllers carry prefixes like 7CP (CPUs) or 7IF (interface modules). Anything labeled “7AC… CANbus controller” is almost certainly mislabeled.
If You Actually Need a B&R CANbus Controller
The genuine CAN-capable products in the B&R portfolio include:
- System 2003 CPUs with integrated CAN — for example the 7CP476-020 (CPU with 1× RS-232 + 1× CAN bus, four local slots integrated) and the 7CP570.60-1 (Celeron-300-compatible CPU, 64 MB DRAM, with RS-232 programming interface and aPCI slot for optional CAN/fieldbus modules).
- System 2003 CAN interface modules in the 7IF series, which plug into the aPCI slot of a CPU to add CAN or CANopen channels.
- X20 system — the X20BC0083 is a true CAN-bus bus controller for the X20 I/O rack, and the X20CS1070 provides a CAN interface for X20 CPUs; X20 interface modules with 2× CAN at up to 1 Mbit/s are also available.
- X90 mobile controller — a rugged CAN-capable controller for off-highway and mobile machinery.
If the machine you are servicing uses a System 2003 rack and you need to restore CAN communication, the 7AC020.9 will not do that job — it only covers an empty slot.
Sourcing the 7AC020.9
As a passive accessory from a legacy line, the 7AC020.9 is obsolete from B&R’s active catalog but is still obtainable through the surplus/MRO channel:
- B&R official product page — lists the part with a downloadable datasheet (login required).
- GSAT International — lists it as “B&R System 2003 bus cover accessory, 1 piece, covers unused bus rack position,” availability on enquiry.
- Classic Automation — stocks the companion 7AC010.9 (5-pc pack) under the System 2003 accessory category.
- Moore Automation and similar surplus dealers — list the 7AC020.9 among their B&R inventory, typically shipped from EU/Asia warehouses with a 12-month warranty on the physical part.
