Siemens TI545 to OP177B HMI: Serial and Ethernet Setup

Overview

Pairing a SIMATIC TI545 CPU (catalog 505-1106) with a SIMATIC OP 177B operator panel is a routine brownfield integration, but the path you take is determined entirely by the OP 177B variant on the shelf. The monochrome "DP mono" model is limited to serial (RS-232/RS-422) and PROFIBUS-DP, while the "PN/DP color" model adds a 10/100 Mbit PROFINET (Ethernet) port. The TI545 covers both paths: the on-board 15-pin D-sub serial port for the DP mono, and the 505-2572 or 505-2572A Ethernet TCP/IP communication card for the PN/DP color. Selecting the correct interface card, setting the CPU DIP switches to a known state, and configuring the OP 177B driver in WinCC flexible yields a deterministic link without a third-party gateway.

This reference consolidates the field-proven cabling, DIP-switch, and HMI configuration settings used to bring up a TI545/OP177B pair. Use the SIMATIC TI545/TI555 System Manual as the source of truth for hardware specifications and the SIMATIC 545 Technical Product Description for module selection, I/O slot rules, and card compatibility lists.

Prerequisites and Hardware Identification

Confirm the following before powering up the panel:

• TI545 base rack with a 505-1106 CPU installed and passing its power-on self-test. The "OK" LED on the CPU must be solid green, with no fault codes blinking on the front diagnostic display.
• OP 177B variant verified on the side nameplate. The MLFB distinguishes the two models:
  • DP mono (5.7" STN, 4 grayscales): 6AV6642-0BA01-1AX0 — RS-485 PROFIBUS-DP and RS-232 only.
  • PN/DP color (5.7" TFT, 256 colors): 6AV6642-0DC01-1AX0 — PROFINET, RS-485 PROFIBUS-DP, and RS-232.
• Ethernet path: a 505-2572 (legacy) or 505-2572A (current production) Ethernet TCP/IP communication card installed in a free slot of the TI545 rack. The "A" revision adds faster SRAM and is required for projects above approximately 4,000 tags.
• Serial path: a shielded RS-232 or RS-422 cable with 15-pin male D-sub on the TI545 side and 9-pin male D-sub on the OP 177B side. Use a TI 505 serial-to-OP cable or build per the table in the Serial Connection section below.
• Configuration software: WinCC flexible 2008 SP3 or later. WinCC flexible is the only engineering tool that supports the OP 177B; TIA Portal does not target this panel family. For TI545 project work, use TISOFT or 505 Workstation (SoftShop) to view and change serial port settings if the DIP switches have been altered from default.

Communication Path Selection

Choose the path that matches the OP 177B variant:

If you have the DP mono OP 177B, you are limited to a serial link. The on-board TI545 serial port can be used directly. PROFIBUS-DP requires the 505-2580 / 505-2580A DP master card on the TI545 side and an RS-485 PROFIBUS cable to the OP 177B. For the PN/DP color model, Ethernet is the preferred path because the link is faster, supports the full tag count of typical WinCC flexible projects, and lets you use existing plant Ethernet infrastructure without a dedicated point-to-point cable.

Serial Connection: RS-232/RS-422 (DP Mono OP 177B)

The TI545 CPU 505-1106 provides one serial port on a 15-pin male D-sub (DB-15M) on the front of the module. By factory default, this port operates at 19200 baud, 8 data bits, no parity, 1 stop bit (19200 8N1), with the TI proprietary serial protocol. The protocol selection and baud rate are set by the CPU DIP switch bank, not by the HMI. If the DIP switches have not been changed since the PLC left the factory, 19200 8N1 is what the OP 177B will see and what you should configure in WinCC flexible.

To use the serial port with an OP 177B DP mono panel:

1. Verify that the DIP switches on the 505-1106 CPU are in their factory positions. Out-of-the-box, the switches configure port 1 for 19200 8N1 RS-232 with RTS/CTS handshaking, which matches the OP 177B serial default. If the switches have been changed, either restore factory or reconfigure WinCC flexible to match the live setting.
2. Connect a shielded serial cable from the TI545 15-pin serial port to the OP 177B 9-pin RS-232 (IF1B) port. Recommended wiring for RS-232 null-modem operation:

   TI545 DB-15M Pin	Signal	OP 177B DB-9M Pin
   2	SD (Send Data / TXD)	2 (RXD)
   3	RD (Receive Data / RXD)	3 (TXD)
   4	RTS	8 (CTS)
   5	CTS	7 (RTS)
   7	Signal Ground	5 (GND)
   Housing	Shield / Chassis	Housing

3. Confirm that handshaking mode is set to RTS/CTS in both the TI545 port configuration and the OP 177B transfer settings. Mixing hardware and software handshaking is a common cause of intermittent communication drops that look like cable faults.
4. Bond the shield to chassis ground at one end only, to break ground loops. Do not allow the shield to carry logic ground, and do not bond both ends — this invites 50/60 Hz circulating current and corrupts data.

For RS-422 (4-wire differential) operation, the OP 177B IF1A port is required. RS-422 is preferred for cable runs greater than 15 m (50 ft) or in electrically noisy panels with VFDs and large contactors. The TI545 serial port is RS-422 capable when DIP switches select RS-422 mode; consult the TI545/TI555 System Manual Section 4 for the exact switch positions for the active protocol on your CPU firmware revision.

Ethernet Connection: 505-2572 / 505-2572A (PN/DP Color OP 177B)

The 505-2572 and 505-2572A Ethernet TCP/IP communication cards plug into any free I/O slot of the TI545 base rack and provide an RJ45 10Base-T (505-2572) or 10/100Base-TX (505-2572A) interface. From the perspective of the OP 177B PN/DP color variant, the TI545 appears as a TCP/IP server. The card supports SRTP (Siemens Real-Time Transport Protocol) and Modbus TCP master/server modes; for OP 177B integration, SRTP is the default and is selected in WinCC flexible.

Card comparison:

For new builds, install the 505-2572A. The 505-2572 is fully functional but is limited in tag count and connection count for OP 177B projects that exceed its performance envelope. The "A" revision is also the only card that supports a 100 Mbit link, which is helpful when the OP 177B and the engineering station are on the same switched network.

To commission the Ethernet path:

1. Insert the 505-2572 / 505-2572A into a free slot and power-cycle the rack. Confirm the card's "OK" LED is solid green and that TISOFT or 505 Workstation "Configure I/O" recognizes it.
2. Configure the card's IP address, subnet mask, and gateway using TISOFT or 505 Workstation. Use an address on the same subnet as the OP 177B — for example, TI545 = 192.168.1.10 / 255.255.255.0, OP 177B = 192.168.1.20 / 255.255.255.0. Avoid 192.168.0.0/16 overlaps with corporate networks and never assign a card to a public IP range.
3. Patch a standard Cat 5e (or better) crossover or straight-through cable between the 505-2572A RJ45 jack and the OP 177B PROFINET (X1) port. Either cable type is acceptable on modern auto-MDI/MDIX Ethernet PHYs, but a crossover is the conservative choice for direct point-to-point links.
4. On the OP 177B, configure the PROFINET (X1) interface with a static IP in the same subnet, or enable DHCP if your plant's DHCP server is configured to hand out fixed leases for the panel.
5. Configure a PROFINET device name on the OP 177B even if you are not using PROFINET IO — the OP 177B PROFINET stack uses the device name for identification, and a mismatch produces "PROFINET name conflict" errors at boot.

DIP Switch Configuration on the TI545

The 505-1106 CPU has an 8-position DIP switch (SW1) bank on the front of the module that controls serial port parameters and certain CPU mode bits. Refer to the SIMATIC TI545/TI555 System Manual for the exact switch positions and their functions, since the assignment has been revised across CPU firmware revisions.

The factory default — which is what the PLC ships with — configures the on-board serial port for 19200 baud, 8 data bits, no parity, 1 stop bit, RS-232 electrical level, RTS/CTS handshaking, and the TI proprietary protocol. Most OP 177B serial drivers are pre-configured for these values, so a factory-fresh TI545 will talk to a factory-fresh OP 177B without any DIP switch changes. If a previous integrator has changed the switches, restore them to the positions documented in the system manual or reconfigure WinCC flexible to match the new baud rate, parity, and protocol.

OP 177B Port Pinout and Cabling

The OP 177B has up to three physical ports on the bottom of the unit. The naming varies by variant:

For an Ethernet-to-PN/DP color OP 177B link, use any standard shielded Cat 5e or better patch cord. For serial, use the wiring table in the Serial Connection section. For PROFIBUS-DP, use a Siemens purple PROFIBUS cable (6XV1830-0EH10 or equivalent) with 9-pin D-sub PROFIBUS connectors, terminating the bus at both ends with 220 Ω / 330 Ω terminators. Verify that the OP 177B termination is enabled in the panel's hardware setup if it is the bus end device.

WinCC Flexible Project Configuration

Open WinCC flexible 2008 SP3 (or the latest service pack that supports the OP 177B) and either create a new project or open the existing project. Configure the connection as follows:

1. In the project tree, expand "Connections" and double-click "Connection_1".
2. Set the "Communication driver" to "SIMATIC TI545/TI555 Serial" (for serial) or "SIMATIC TI545/TI555 Ethernet" (for Ethernet via 505-2572A). Do not select "SIMATIC S7 Ethernet" or any S7 driver — they will not resolve TI545 points.
3. For serial: set baud rate to 19200, parity to None, data bits to 8, stop bits to 1. Disable any software flow control. Match the TI545 DIP-switch setting exactly.
4. For Ethernet: enter the IP address of the 505-2572A card. The default port for SRTP is 102. The "Station address" field accepts the rack/slot pair of the 505-2572A in the TI545 I/O map.
5. Add tags by browsing the TI545 point database. The OP 177B driver for the TI545 supports V-memory, K-memory, and discrete I/O references (e.g., V40001 for a real value, C101 for a discrete input). Use the WinCC flexible point picker to confirm the address syntax — V40001 is a 16-bit word, V40001-F is the same word as a float, and C101 is a single bit.
6. Compile the project (Project → Compiler → All) and resolve any warnings. "Unconnected tag" warnings are acceptable for tags that are intentionally not yet wired, but driver errors must be fixed before transfer.
7. Transfer the project to the OP 177B via Ethernet or serial. If using Ethernet, enter the panel's IP address in the transfer dialog. If using serial, the OP 177B must be in "Transfer" mode — Start Center → Settings → Transfer → enable.

If the OP 177B is on PROFINET and the network is large, configure the panel's PROFINET device name in WinCC flexible under "Device configuration → PROFINET interface" before transfer. A PROFINET device name mismatch is one of the top three causes of an OP 177B failing to come up on PROFINET, even when the IP address is correct. Use the TIA Portal PST (Primary Setup Tool) or any PROFINET naming tool to assign a unique name on the network.

LED Diagnostics on the 505-2572A and OP 177B

Use the front-panel LEDs to localize a fault before reaching for a cable tester.

If the 505-2572A OK LED is red, the card is not properly seated or the I/O map is inconsistent. Eject the card, reseat, power-cycle, and re-run "Configure I/O" from TISOFT. If the LED remains red, the card may need a firmware reload.

Verification and Commissioning

After the cable is in place and the WinCC flexible project is compiled and transferred, verify the link with a known-good tag before trusting live process data:

1. Power-cycle the OP 177B. Watch the boot screen — if it completes without a "Communication error" banner, the HMI itself is healthy.
2. On the OP 177B, navigate to "Start Center → Settings → Network" (or "PROFINET IO" for DP color) and confirm the IP address and PROFINET device name are applied. If the field is empty, the transfer did not write the network configuration.
3. For Ethernet, ping the 505-2572A from the OP 177B's diagnostic page or from a laptop on the same subnet. A reply confirms Layer 3 reachability. If the ping times out, the issue is at Layer 1 or 2 (cable, switch port, or IP) and not at the WinCC flexible driver.
4. For serial, use the OP 177B's "Transfer" menu to start a manual transfer and observe the status line for "Connecting..." followed by "Connected". A persistent "Connecting..." indicates a cable, baud, or handshaking mismatch.
5. Add a simple "Status" screen in WinCC flexible with a numeric tag tied to a known-good TI545 word (e.g., V40001). If the value updates when you force a value in TISOFT, the round-trip is working.
6. Force a bit in the TI545 from TISOFT and verify the corresponding indicator on the OP 177B screen changes state within one second (Ethernet) or two seconds (serial at 19200 8N1). A round-trip time above 3 s indicates that the driver is polling slowly or that the 505-2572 (non-A) is at its connection limit.

Safety and Pre-Commissioning Checks

Before powering up the panel in a live process area, complete the following:

• Verify that the 24 V DC supply to the OP 177B is within the rated 20.4–28.8 V DC range. A weak supply is the leading cause of intermittent panel reboots that look like communication errors.
• Confirm protective earth is bonded to both the OP 177B and the TI545 rack at the same panel ground bus. Star-ground the panel rather than daisy-chaining.
• With the TI545 in PROGRAM mode (CPU mode switch in STOP/PROGRAM), perform a dry run of the project transfer. This prevents a misconfigured project from writing to live outputs.
• Identify the "first tag" — a discrete output on the TI545 that the OP 177B is allowed to toggle. Do not authorize writes to safety-relevant or motion-control tags from the HMI until the round-trip is verified.
• Document the final IP addresses, PROFINET device names, baud rates, and DIP-switch positions in the project file. A field engineer in 2028 will not have your memory of how the link was commissioned.

Spare Parts and Migration Notes

Keep the following on the shelf for TI545/OP177B service calls:

• One spare 505-2572A Ethernet TCP/IP card (current production).
• One spare 505-1106 CPU with matching firmware revision. CPU firmware revisions are not always cross-compatible; verify with TISOFT before swapping in a spare.
• One spare OP 177B PN/DP color panel with a current firmware image. OP 177B firmware is updated via WinCC flexible 2008 SP3 and above; the latest image is V12.01.xx or later.
• One Cat 5e patch cable, one PROFIBUS drop cable with connector, one DB-15 to DB-9 null-modem serial cable, one DB-9 gender changer.

When migrating from a 505-2572 to a 505-2572A in an existing project, the IP configuration and TISOFT project must be re-loaded onto the new card. The two cards are pin-compatible and slot-compatible, but the firmware image format differs. Flash the new card with the latest firmware using TISOFT's "Update 505-2572A" utility before returning the rack to RUN mode.

Troubleshooting Matrix

FAQ