OP77B to PC Connection: Cable Setup, Transfer Settings and Error Fixes

The Siemens SIMATIC OP77B (6AV6 641-0CA01-0AX0 / 6AV6641-0BA01-0AX0) is an 8-line text/graphic HMI panel in the OP 77 product family. Although the panel exposes both an RS232/PPI port (IF1B) and an MPI/PROFIBUS-DP port (IF2), many field engineers hit the same wall when trying to download a project: WinCC flexible 2008 reports "A connection could not be established. Please check your settings, ports, cable", and the diagnostic LEDs on the cable stay dark. This reference consolidates the official Siemens cable catalog, the OP77B transfer menu, and the WinCC flexible 2008 transfer channel to give you a deterministic commissioning path.

1. Problem Description and Symptoms

The reported symptoms cluster into three failure modes, all originating from the same root: a mismatch between the physical cable, the panel transfer menu, and the WinCC flexible transfer channel.

2. OP77B Hardware Interfaces and Transfer Channels

The OP77B rear panel exposes two physical interfaces, configured in the panel's Transfer menu (reached via the operating system's Control Panel on the panel itself, or by holding the bottom-right function key while powering on):

• IF1B – Sub-D 9-pin male, RS232/PPI protocol. Default for project transfer.
• IF2 – Sub-D 9-pin female, MPI / PROFIBUS-DP up to 1.5 Mbit/s. Used for HMI-to-PLC communication; not a transfer channel on OP77B.

The transfer menu offers two configurable channels. Channel 1 corresponds to IF1B (RS232/PPI) and Channel 2 to IF2 (MPI/DP). Both channels can be enabled independently, but only one transfer source can be active per session.

3. Approved Cable Catalog for OP77B Transfer

The Siemens catalog numbers below are extracted from the official S7 cabled accessories list (see the Siemens entry ID 1137380 - Cables for connecting SIMATIC Panels). For the OP77B, only cables marked recommended in the table below are sanctioned for project transfer.

4. Root Cause Analysis of the Reported Error

The original user case combines all three failure modes at once:

1. Wrong cable class. The 6ES7 972-0CA23-0XA0 PC-Adapter V5 is an MPI/DP master, not an RS232/PPI transfer cable. The OP77B firmware rejects transfer requests coming from a bus master on IF2 because the panel is not configured as a slave on a DP segment.
2. USB-to-RS232 adapter in the path. Off-the-shelf USB-to-serial converters re-map COM port numbers and frequently miss the DSR/DTR handshake transitions that the OP77B requires to enter transfer mode. LED stays dark because the panel never sees a valid CD/RTS edge.
3. Transfer menu mis-configured. Channel 2 was set to MPI/DP with address 1 and 19.2 kbit/s, but the cable and the WinCC transfer are pointed at Channel 1 (RS232/PPI). When both channels are mis-matched the panel never advertises its transfer service to the WinCC transfer tool.
4. Image/Project version skew. When the user switched to a direct USB cable, WinCC flexible 2008 detected image V07.02.02.0 on the panel while the project was compiled for V07.03.xx, triggering the "version of the panel is not good" message.

Each of those four items independently blocks the download. Resolving the fault requires closing every one.

5. Solution Path A – Use the PC/PPI USB Cable (Recommended)

The most robust path is to drop the PC-Adapter V5 entirely and use the 6ES7901-3BF00-0XA0 (or its modern equivalent 6ES7901-3CP30-0XA0). The PC/PPI cable is bus-powered from the PC's USB port and integrates a Siemens S7-200/300-class PPI master that speaks the same protocol the OP77B expects on IF1B.

5.1 Prerequisites

• PC/PPI USB cable 6ES7901-3BF00-0XA0 (or -3CP30-0XA0).
• WinCC flexible 2008 SP3 with the latest hotfix (HF7 or later) installed.
• ProSave V13 or later (installed alongside WinCC flexible) for image management.
• Administrator rights on the PC to install the USB-Serial driver (FTDI 2.08.28 or later for the 3CP30 revision).

5.2 Configure the Cable DIP Switches

The PC/PPI cable has an 8-position DIP switch on the housing. The valid settings for OP77B transfer are:

The 6ES7901-3CP30-0XA0 is configured entirely through the Windows device properties (baud rate selectable in the driver) so most of the above switches are inactive; default 18750 bit/s is usually the lowest-friction choice.

5.3 Configure the OP77B Transfer Menu

Power on the OP77B. During boot, tap the centre of the screen or press the lower-right function key combination to enter the Windows CE Control Panel equivalent. Navigate to Transfer.

1. Channel 1:
   • Serial Setting: Enable, Remote Control = ON
   • Select Channel 1: RS232 / PPI
   • Baud rate: 18750 or 57600 (must match cable)
   • Address: 1
2. Channel 2:
   • Disable, OR set to MPI/DP at 19.2 kbit/s address 1 (the panel will not enter transfer over MPI but the PLC will still see the panel)

Save and exit; the panel reverts to normal operation and now listens on IF1B for a transfer request.

5.4 Configure the WinCC flexible 2008 Transfer

Open the project in WinCC flexible, then Project → Transfer → Transfer Settings:

• Mode: RS232 / PPI Multi-Master Cable
• Port: COMx (the COM port assigned to the PC/PPI cable in Windows Device Manager)
• Speed: Start with 57600; fall back to 18750 if the panel times out
• Address: 1 (must match the OP77B)

5.5 Trigger the Download

1. Connect the PC/PPI cable between the PC's USB port and the OP77B's IF1B (sub-D male on the panel).
2. Power on the OP77B and wait for the project screen to appear.
3. In WinCC flexible click Transfer → Download to Target System. The PC/PPI cable LED will toggle and the panel will show Transfer....

6. Solution Path B – Direct RS232 Zero-Modem Cable to PC COM Port

When the workstation still has a true COM port (or a verified chipset-grade PCMCIA / ExpressCard RS232 adapter), the most reliable path is a true crossed RS232 cable: 6ES7901-1BF00-0XA0 (RS232 / zero-modem cable, 6 m). This cable crosses TX/RX and RTS/CTS lines exactly as the OP77B expects.

6.1 Adapter Pitfalls

6.2 WinCC flexible Transfer Settings for the Zero-Modem Path

• Mode: RS232 / PPI Multi-Master Cable (WinCC flexible automatically configures the serial port for 19200-8-E-1 when this mode is chosen)
• Port: COM1 / COM2 – whichever is the physical port
• Speed: 9600 / 19200 / 38400 – try in that order if the first attempt times out

6.3 OP77B Menu Settings for the Zero-Modem Path

• Channel 1: RS232 / PPI, baud 19200, address 1, Remote = ON
• Channel 2: keep as MPI/DP if a PLC is on IF2, otherwise disable to avoid bus collisions

7. Solution Path C – Resolving the "Version of the Panel Is Not Good" Error

This error appears when the *.hmi file compiled in WinCC flexible targets an image version newer (or older) than what is currently flashed on the OP77B. Typical field combination: image V07.02.02.0_01.67 on the panel, project compiled for V07.03.00.0_01.85.

7.1 Path C1 – Recompile the Project for the Installed Image

In WinCC flexible 2008, open the project, then Project → Device → Device Version and select the image version present on the panel. Recompile and re-download. This is the fastest fix and avoids any flash operation.

7.2 Path C2 – Reflash the Panel Image Using ProSave

1. Connect the PC to the OP77B via the PC/PPI USB cable.
2. Launch ProSave, choose Panel type = OP77B, Connection = PPI, Port = COMx.
3. Select the correct image (e.g. OP77B_V07_03_00_01.img) from the WinCC flexible installation folder \HmiImages\OP77B\.
4. Click Update OS and confirm the boot loader reboot. The panel displays Booting...; do not power off.
5. After the update, re-enter the Transfer menu and re-enable Channel 1 (the reflash defaults to a stopped state).
6. Return to WinCC flexible and re-attempt the project download.

Detailed steps are in the Siemens ProSave documentation – ID 23634485.

8. Cable and Adapter Cross-Reference Matrix

The table below summarises which cable is sanctioned for which use case, and at which baud rate. When the field report is ambiguous, both the standard and the more aggressive setting are listed.

9. Verification Procedure

After applying the settings, perform the following verification sequence to confirm the panel is in transfer state and the WinCC flexible session is healthy.

1. Visual state on OP77B: After saving the Transfer menu, the panel should display Transfer... automatically if Channel 1 Remote = ON and a valid cable is connected. If the panel returns to the project, Channel 1 is not enabled or the cable is not detected.
2. LED on PC/PPI cable: The activity LED toggles within 1–2 s of pressing Download to Target System. A steady-off state indicates a hardware or COM-port problem.
3. WinCC flexible status bar: Reads "Connecting..." followed by "Transferring..." and finally "Transfer completed". Any error 0x00030001 = connection failed, 0x00030010 = timeout, 0x00030020 = image version mismatch.
4. Project restart on the panel: After successful download, the OP77B reboots automatically and starts the new project. Confirm the project name in the title bar matches the source.

10. Troubleshooting Matrix

11. Field-Engineer Best Practices

• Always keep one 6ES7901-3BF00-0XA0 PC/PPI USB cable in the service case; it is the lowest-friction transfer path for the OP77B and the OP73, OP77A, TP170A, TP170B micro panels.
• If the PC has no native COM port, prefer a PCMCIA / ExpressCard with a genuine 16C550 UART over a USB/serial dongle. The latter adds latency to the token-passing handshake and exposes the OP77B to spurious 0x00030010 timeouts.
• Document the panel image version on the project cover sheet. When the fielded panel runs V07.02.02.0_01.67 and a backup project on the engineering station was last edited in V07.03.xx, plan a recompile before the next service visit.
• Configure Channel 1 to Remote = ON for unattended transfer, but revert to Remote = OFF once the project is in production to prevent a maintenance laptop from accidentally starting a transfer.
• Verify the back-panel DIP switches of the OP77B before any download. The four switches set write-protection; if any switch is down, the panel will not accept a new project.

12. FAQ