Upgrade Paths for Legacy Allen-Bradley Systems: SLC 500, MicroLogix, 1768, PanelView, FLEX I/O, ControlNet

Quick reference

The numbers above are public Rockwell Automation publications. Each path is detailed below; page numbers refer to the editions TDL uses.

SLC 500 → CompactLogix 5380: keep the wiring, change in steps

Hardware. The 1492 conversion system lets you keep the field wiring: the removable terminal block of the 1746 module plugs straight into a conversion module, with a Compact 5000 module underneath (1492-SG010B p. 3). Every SLC chassis has a matching conversion chassis — 1746-A4/A7/A10/A13 to 1492-CH1746-4/-7/-10/-13 (p. 4) — which bolts into the existing holes without drilling the panel (MIGRAT-PP004C p. 2). Two points must be checked first: 32-point modules split into two 5069 modules (for example 1746-IB32 → 2 × 5069-IB16), and according to 1492-SG010B (p. 9–11), 5069-IF8 and 5069-IY4 accept differential signals only — for 5069-IF8 specifically, the 5069-TD001P edition (2026, p. 26) states that series B inputs are single-ended, so check the module series and the field device wiring before ordering.

Changing in steps. MIGRAT-PP004C describes four steps: convert the program; replace the SLC CPU with a 1747-AENTR adapter so the new controller runs the old SLC I/O over EtherNet/IP (still reversible); replace the remaining hardware; finally replace the I/O with the 1492 system (p. 6–7). The adapter has limits to plan for: 96 Class 1 connections, no rack-optimized connections so each module uses one connection, and it cannot be used in a ControlLogix redundancy system (5069-AP001A p. 11–12).

Controller and memory. 1746-RM003F (p. 17–18) gives a replacement table: most SLC CPUs map to 1769-L24ER-QB1B (5370) or 5069-L306ER (5380); 1747-L543/L553 (64K) map to 1769-L30ER or 5069-L310ER. Rule of thumb: a full 32 KB SLC program becomes about 360 KB on Logix; 64 KB needs a controller of about 800 KB or more (5069-AP001A p. 13).

Program. RSLogix 500 v12 saves straight to an .ACD file; older versions use the RSLogix Project Migrator (1746-RM003F p. 8), targeting version 30 or later (5069-AP001A p. 46–47). The tool produces a syntactically correct program but does not guarantee the original intent: suspect rungs are flagged PCE; indirect file addressing, SFC, STI/DII interrupts, HSC instructions and Modbus MSG are not converted; timers move to a 1 ms time base so presets are multiplied by the old time base (×10 for 0.01 s, ×1000 for 1 s), and every direct read of .PRE/.ACC must be reviewed by hand (p. 50, 61, 73–74). This is the most labour-intensive part, and the reason TDL bench-tests the program before going to site.

MicroLogix

MicroLogix 1500 → CompactLogix 5370 L1/L2. Rockwell lists MicroLogix 1500 as discontinued (MIGRAT-PP015B p. 1). Existing 1769 I/O can only be reused with the L2 family. Differences to plan for: the 5370 has no 120/240 V AC power version, no RS-232 port, and no support for DF1 half-duplex/radio or Modbus RTU; Modbus TCP goes through an MVI69-MNET module (p. 3).

MicroLogix 1000/1100/1200/1400 → Micro800. Converted with the MicroLogix to Micro800 Converter in Connected Components Workbench (2080-RM002D p. 43–48). Not converted: status files, indirect/indexed addressing for S, I and O files, controller and I/O configuration, interrupts, passwords (p. 52); MCR, SQC, SQL and SQO have no equivalent yet (p. 130).

CompactLogix 1768-L4x → CompactLogix 5380

MIGRAT-PP037A gives two options: replace everything with 5380 and Compact 5000 I/O, or keep the existing 1769 I/O as a remote rack through a 1769-AENTR adapter; the new hardware fits most existing panels (p. 3). For the 1769-L3xE controllers (L31, L32E, L35E): see the corresponding row in the quick reference table at the top.

PanelView Standard / Enhanced → PanelView Plus 7

• Application: the .pba file (or the .pva if the .pba is lost) is imported into FactoryTalk View Studio ME, with scaling to the new resolution; results are written to convert.log (2711P-AP006F p. 43–48).
• Communications: PanelView Plus 7 has Ethernet only; applications on serial links must move to EtherNet/IP (2711P-AP005F p. 2, p. 34). DH+, DH-485, Remote I/O, DeviceNet and ControlNet are no longer available on the new terminal (2711P-AP006F p. 55).
• What must be fixed by hand: bit arrays become memory tags, strings are limited to 82 characters, "retain last state" is gone, multistate objects number from 0 instead of 1 (p. 10, p. 45).
• Panel cut-outs: no Plus 7 terminal fits the cut-out of a PanelView 300/300 Micro; some fit directly, others need an adapter kit — and these kits are for the Performance line only (p. 19, p. 39). Replacing an AC-powered terminal with a Plus 7 Standard requires an additional 24 V DC power supply (p. 21).

Upgrading from PanelView Plus 6 to Plus 7 is a different case (migrating a FactoryTalk View ME project).

FLEX I/O → FLEX 5000

FLEX 5000 runs on EtherNet/IP only; Remote I/O, ControlNet and DeviceNet adapters all map to the 5094-AENTR (5094-RM001A p. 14). The controller must be a ControlLogix 5580, CompactLogix 5380/5480 or Compact GuardLogix 5380, with Logix Designer v31 or later — ControlLogix 5570 or CompactLogix 5370 systems must upgrade the controller first (p. 27). The mounting footprint is similar but modules are 10–30 mm taller, and wiring must be moved by hand (p. 13, p. 47). Rockwell classifies this as a solution that requires program changes: analog data changes from INT to REAL, RPI ranges differ (p. 29); some modules have no equivalent (p. 16–20).

ControlNet → EtherNet/IP

ENET-WP003A explains why to move — ControlNet products are moving to Active Mature status; ControlNet bandwidth is fixed at 5 Mbps; integrated motion and CIP Safety devices exist only on EtherNet/IP; network redundancy is replaced by DLR or PRP; ControlNet fibre can usually be reused with new connectors (p. 2–5). The overall procedure and conversion examples are in CNET-RM001A p. 21–27. Choosing between DLR and PRP: see DLR or PRP.

PLC-5 and 1771 Remote I/O

The 1756-DHRIO module lets ControlLogix scan Remote I/O racks (1771-ASB, 1747-ASB, FLEX, PanelView…) and exchange messages over DH+ with PLC-5/SLC (1756-UM514C p. 13–15, p. 101). This allows the processor to be replaced first while the 1771 I/O racks stay during the transition — provided the channel limits are respected: up to 32 rack numbers per channel, but only 16 if the network includes a 1771-ASB/A, 1771-ASB/B, 1771-AS, 1771-DCM or 1771-AF; 57.6/115.2/230.4 kbps correspond to total (daisy-chain) cable lengths of 3,048/1,524/762 m (p. 102–103). Note: Rockwell discontinued the 1756-DHRIO on 31/12/2024 (product page on rockwellautomation.com) — this route suits plants that still hold the modules; otherwise, move the I/O straight to EtherNet/IP. Converting the PLC-5 program has its own article: PLC-5 to ControlLogix migration.

How TDL does it

Survey and fix the path according to the documents for the exact product line in service; convert the program and bench-test it; FAT; where the system can be split into sections, replace them one at a time in shutdown windows set by the plant. Replacing a single CPU or module follows the same process on a smaller scale.