SLC 500 1747-L30A DH-485 Connection: PIC, UIC, RSLinx Setup

Problem Overview

The Allen-Bradley 1747-L30A is a fixed-style SLC 500 processor that ships with a built-in DH-485 communication port (Channel 0) and a 9-pin RS-232 Channel 1 port. When the only available PC is modern, lacks a true DB-9 serial port, or runs a 64-bit Windows 7/8/10/11 operating system, engineers routinely hit three roadblocks: (1) the 1747-PIC converter cannot enumerate because no native COM port exists, (2) the legacy "AIC+" or "1747-PIC/AIC+" driver has been removed from recent RSLinx Classic builds, and (3) the 1747-UIC driver is silently filtered from 64-bit RSLinx installers. The result is a visible driver list, an installed USB device, but no way to bring the 1747-L30A online in RSLinx or RSLogix 500.

This reference documents the available communication paths for the 1747-L30A, the exact RSLinx Classic versions that retain the legacy DH-485 drivers, the Windows OS boundaries, and the verified commissioning steps for each option.

Hardware Identification: 1747-L30A

Before selecting an interface, confirm the exact catalog and firmware revision of the processor. The L30A is electrically and functionally distinct from the L20, L40, and the later L30B/L30C revisions.

Available Communication Paths

Three physical options exist for connecting a PC to the 1747-L30A Channel 0 (DH-485). Channel 1 (RS-232) supports DF1 full-duplex point-to-point and is the simpler path when the PC has a real COM port, but DH-485 multi-drop and the full RSLinx browse tree require Channel 0.

RSLinx Classic Driver Compatibility Matrix

The RSLinx Classic "Configure Drivers" dialog is the first place to look. The required driver for the 1747-PIC and 1747-AIC(+) is enumerated as 1747-PIC/AIC+ Driver. For the 1747-UIC, the driver is USB – 1747-UIC DH485 Device and depends on a Windows-side HID-compatible installation of the UIC utility.

Path A: 1747-PIC (RS-232) on a Legacy PC

The 1747-PIC converts RS-232 to DH-485 and draws power from the PC's COM port or the SLC's Channel 0. It is the cheapest legacy option and the one most affected by the disappearance of native serial ports on modern hardware.

1. Verify the host PC has a true RS-232 COM port (DB-9 male, ±12 V swing). USB-to-serial adapters do not work; the 1747-PIC requires the hardware handshaking lines DTR/RTS to source 5 V supply current to the converter.
2. Install RSLinx Classic v3.74 (or v3.80 32-bit) on Windows XP SP3 or Windows 7 32-bit. Avoid 64-bit Windows; the driver is filtered out.
3. Launch RSLinx and open Communications > Configure Drivers. Select 1747-PIC/AIC+ Driver and click Add New.
4. Name the driver (e.g., DH485_PIC), select the COM port, and set the baud rate to 19200 (default). Click Apply.
5. From RSLogix 500, select Comms > System Comms. The AB_PIC-1, DH485_PIC driver should appear under the AB_ETH/IP-1 node tree. Double-click to go online.

Verification: In RSLinx, run Edit > Who's Active (or RSWho). The 1747-L30A should appear at node 1 (default). If the node address was changed, use Auto Browse to scan nodes 0–31.

Path B: 1747-UIC (USB) on a 32-bit PC

The 1747-UIC is a USB-to-DH485 converter with built-in link coupler (no separate AIC required). It is the cleanest path for a laptop without serial ports, but it is restricted to 32-bit Windows because the HID-class driver shipped with RSLinx is signed only for x86.

1. Confirm the host is a 32-bit OS. On Windows 10/11 64-bit, the 1747-UIC will enumerate as a USB Human Interface Device, but RSLinx will refuse to bind the USB – 1747-UIC DH485 Device driver.
2. Install RSLinx Classic v3.80 (32-bit) or v3.90 (32-bit). Reboot.
3. Plug the 1747-UIC into a USB 1.1 or 2.0 port. Windows should detect the device; do not rely on "USB Serial Converter" drivers from FTDI or generic hubs.
4. In RSLinx, open Configure Drivers and add USB – 1747-UIC DH485 Device.
5. Wire the 1747-UIC's DH-485 terminals (1, 2, 3, 4 — shield, drain) to the L30A Channel 0 mini-DIN. Observe polarity: terminal 1 = shield, 2 = SHD, 3 = DATA B, 4 = DATA A.
6. Click Start on the driver; the Auto-Configure should report the active nodes.

Verification: Use RSWho to confirm visibility of the L30A. If the driver starts but the tree is empty, verify termination (150 Ω across terminals 3 and 4) is present at both ends of the DH-485 trunk and that the UIC's node number is unique (default 0).

Path C: PCMCIA / PC Memory Card (PCMK)

The 1784-PCMK (CardBus) and 1784-PMCK (PCMCIA) cards place the PC directly on the DH-485 trunk with no converter in between. They are still the lowest-latency option but are limited to laptops with PC Card slots, which excludes most post-2012 hardware.

1. Insert the 1784-PCMK into a CardBus slot. Windows should detect 1784-PCMK as a network adapter.
2. Install RSLinx Classic 32-bit and add the 1784-PCMK Driver from Configure Drivers.
3. Assign a unique DH-485 node address (1–31) to the PC; the L30A default is 1.
4. Connect the card's 8-pin mini-DIN directly to the L30A Channel 0, or to a 1747-AIC for multi-drop isolation.

Verification: RSLinx RSWho should show [1784-PCMK, port1] and the L30A underneath. The PCMK propagates the entire DH-485 segment into the RSLinx tree as if it were a native node.

Channel 1 (RS-232) DF1 Alternative

If the goal is online programming only and DH-485 multi-drop is not required, the L30A's Channel 1 (DB-9 male) supports DF1 full-duplex to a single PC. This bypasses all DH-485 driver issues.

1. In RSLinx, add the RS-232 DF1 Devices driver.
2. Set the COM port to 19200, 8-N-1, no flow control (or hardware).
3. Configure the L30A Channel 1 in RSLogix 500: Channel Configuration > System > Chan 1 – System > DF1 Full Duplex, baud 19200, node 1, no parity.

Verification: RSWho shows AB_DF1-1, COM1, 1920 with the L30A underneath. This path works on 64-bit Windows as long as the COM port is real or a properly signed USB-to-serial adapter (FTDI FT232, CP2102N) with the matching VCP driver.

Troubleshooting Matrix

Firmware and Channel Configuration Checks

Before troubleshooting cabling, verify the L30A Channel 0 parameters from the front-panel keyswitch or via a previous online session. Default values that often cause silent failures:

• Node Address: 1 (valid range 0–31 decimal)
• Baud Rate: 19200 (valid: 1200, 2400, 4800, 9600, 19200)
• Max Node: 31 (must be ≥ L30A node)
• Token Hold Factor: 1
• DH-485 Baud: matches the trunk (do not mix 9600 and 19200 devices)

If the L30A's node is unknown, the key-switch procedure is: keyswitch to RUN, hold CLR while cycling power, then enter node number using the thumbwheel or RSLogix (if available). Avoid nodes 0, 1, and 2 if any panel device uses them.

Modern PC Fallback: Industrial Communication Gateways

When neither a legacy PC nor a 32-bit install is acceptable, a third-party protocol gateway can bridge DH-485 to EtherNet/IP, allowing a 64-bit Windows 10/11 PC running RSLinx Classic 64-bit (or FactoryTalk Linx) to browse the L30A indirectly. Common gateway platforms include:

• ProSoft Technology PTQ-DH485 (SLC to EtherNet/IP)
• SST EIP-DH485 (Woodhead / Molex)
• Anybus X-gateway DH485 (HMS Industrial Networks)

These gateways present the DH-485 segment as a Class 3 EtherNet/IP target, eliminating the need for the legacy PIC/UIC drivers entirely. Latency rises by one scan cycle (typically 5–20 ms), which is acceptable for programming and HMI polling but not for high-speed interlocking.

Safety and Handling Notes

• DH-485 cabling must use shielded twisted pair (Belden 9841 or equivalent), drain bonded at one end only.
• Maximum trunk length is 1219 m (4000 ft) at 19200 baud; 3048 m (10000 ft) at 1200 baud.
• Maximum of 32 nodes per segment; star topology is not allowed — use daisy chain only.

Recommended Decision Flow

1. If a real DB-9 serial port and 32-bit Windows are available → use the 1747-PIC.
2. If no serial port but 32-bit Windows is available → use the 1747-UIC.
3. If only 64-bit Windows and a PC Card slot exist → use the 1784-PCMK (32-bit RSLinx via XP Mode if necessary).
4. If only 64-bit Windows on modern hardware exists → deploy a DH-485-to-EtherNet/IP gateway.
5. For point-to-point programming only → use Channel 1 DF1 over a USB-to-serial adapter.