Allen-Bradley AB-EtherNet (PLC-5 / SLC-500 Legacy)
AB-EtherNet is the Ethernet communication method used by Allen-Bradley's legacy PLCs — PLC-5, SLC-500, and MicroLogix. It is a protocol from the era before CIP / EtherNet/IP became the standard, and it carries PCCC (Programmable Controller Communication Commands) messages over Ethernet.
This gateway communicates through the AB-ETH adapter of the common integration engine.
For AB's current series — ControlLogix / CompactLogix (Logix5000) — see the EtherNet/IP page. AB-ETH is only for the preceding PLC generation.
| Series | Page |
|---|---|
| PLC-5 / SLC-500 / MicroLogix 1100–1400 | This page (AB-ETH) |
| ControlLogix 5550–5580 / CompactLogix 5370–5380 | EtherNet/IP |
Registration form entries
| Field | What to enter | Example |
|---|---|---|
| IP address | The PLC's IP | 192.168.0.10 |
| Port | CSP port — not EtherNet/IP's 44818 | 2222 |
| Station (station) | DF1 destination station number | 1 (default) |
| Response timeout (read-timeout) | Response wait (ms) | 3000 |
AB-ETH uses CSP over TCP/2222. 44818 is the EtherNet/IP (CIP — ControlLogix)
port and belongs to a different driver. This driver is read-only (write is not supported).
On the PLC side, the Ethernet module (e.g., PLC-5/E, 1747-AENTR, 1761-NET-ENI) must be enabled and assigned an IP in RSLogix 5 / RSLogix 500.
PLC address notation for tags
This driver supports word / bit reads of Integer (N) data files. Format:
N<file>:<element>[/<bit>]:<TYPE> — TYPE is mandatory.
| Notation | Meaning |
|---|---|
N7:0:WORD | Integer file 7, element 0 (16-bit unsigned) |
N7:0:INTEGER | Same location, 16-bit signed |
N7:3:DWORD | 32-bit starting at element 3 (2 words, unsigned) |
N7:3:DINT | 32-bit signed starting at element 3 |
N7:5:FLOAT | 32-bit float starting at element 5 |
N7:10/0:SINGLEBIT | Bit 0 of element 10 (Boolean) |
Supported TYPE: WORD(u16) / INTEGER(s16) / DINT(s32) / DWORD(u32) / FLOAT /
LONG(s64) / QWORD(u64) / DOUBLE / BOOL / SINGLEBIT(bit). If TYPE is omitted,
the read fails and the value stays empty.
F8:0, B3:0/0, T4:0.ACC, ST10:0, etc.) are not supportedFloat(F) / Bit(B) / Timer(T) / Counter(C) / Status(S) / String(ST) file notations are not
accepted by this driver. Mirror float values into an N file in the ladder logic and read them
with N<file>:<elem>:FLOAT. Strings (ST) are not supported.
Data type matching
| Value in the PLC | Data type | Address example |
|---|---|---|
| 16-bit integer (signed) | Integer | N7:0:INTEGER |
| 16-bit unsigned | Word | N7:0:WORD |
| 32-bit integer | DInt (signed) / DWord (unsigned) | N7:3:DINT |
| 32-bit float | Float | N7:5:FLOAT |
| Bool / bit | Boolean | N7:10/0:SINGLEBIT |
Common problems and solutions
| Symptom | Possible cause | Solution |
|---|---|---|
| "Connection refused" | Registered with port 44818 / no Ethernet module installed | Check that the port is 2222; add an external Ethernet adapter such as a 1761-NET-ENI |
| "File not found" | The data file does not exist in the PLC | Check the file number under Data Files in RSLogix 500 |
| Corrupted values | Mismatch between the address TYPE and the actual width | Distinguish :WORD(16-bit) ↔ :DWORD/:FLOAT(32-bit) |
F8:0 / T4:0.ACC cannot be read | Notations other than N files are not supported | Mirror to an N file in the ladder logic, then register with N<file>:<elem>:<TYPE> |
| Only MicroLogix fails | Some MicroLogix 1000 units do not support PCCC over Ethernet | Replace with a 1100/1400 that has Ethernet, or go through a serial NET-ENI |
Migration notes
PLC-5 / SLC-500 are discontinued and are no longer sold new by RA (Rockwell). When you replace an aging line with ControlLogix / CompactLogix, move on to the procedure on the EtherNet/IP page. Just before the swap, using PlantPulse's View collection history to back up the as-is data is useful for validating the new PLC against the old one.
Next steps
- The AB-ETH examples in Advanced — REST API
- If ControlLogix units are mixed into the same site, refer to the EtherNet/IP page as well