Siemens OP7-DP Program Upload via Serial Cable: Pinout & Transfer

Siemens OP7-DP Program Upload via Serial Cable: Pinout, Transfer Mode, and Compatibility Reference

The Siemens SIMATIC OP7-DP operator panel, identified by MLFB (order number) 6AV3607-1JC20-0AX1, is a text-and-graphic HMI from the OP7 family that integrates a Profibus-DP interface for direct connection to SIMATIC S7 PLCs. Although the device was cancelled from the Siemens catalog effective 1 October 2007, it remains in service across legacy machine fleets worldwide. This reference consolidates the field-proven procedure for uploading the panel configuration, the serial cable pinout required to perform that upload, the keypress sequence that forces the panel into transfer mode, and the strict compatibility constraints that govern what can and cannot be recovered from the device.

1. Product Identification and Lifecycle Status

The MLFB 6AV3607-1JC20-0AX1 decodes as follows:

Lifecycle facts every maintainer should record on the panel's asset tag:

• Cancellation date: 2007-10-01. Siemens no longer manufactures new units.
• Spare-parts availability: Subject to stock exhaustion; refurbished and pull-out units dominate the secondary market.
• Successor products: SIMATIC OP 77B (6AV6641-0AA11-0AX0), SIMATIC KTP400 Basic (6AV2123-2DB03-0AX0), and later Comfort/Advanced lines. These are not drop-in replacements because the OP7's runtime image is not portable to KTP/Comfort firmware.
• Configuration software: The OP7 is programmed exclusively with ProTool / ProTool Lite (V6.0 or earlier for the OP7 device family). ProTool was superseded by WinCC flexible (2004) and later TIA Portal. None of those newer tools can open OP7 source projects.

2. Communication Interfaces on the OP7-DP

The OP7-DP exposes two physically distinct communication ports:

The Profibus port cannot be used for configuration transfer. Configuration transfer always travels over the RS-232 configuration port (IF1A). This is a frequent source of confusion when engineers assume "DP" means "everything Profibus", or that an MPI/PPI multi-master cable will work.

3. Why a PPI Cable Will Not Work

The Siemens PPI (Point-to-Point Interface) protocol is a multi-drop, 11-bit RS-485 variant used exclusively between a SIMATIC S7-200 CPU and its programming software (STEP 7 Micro/WIN). The PPI cable integrates an RS-485 transceiver and the PPI firmware handshake inside the cable itself.

The OP7-DP configuration port is:

• Electrical: RS-232 (single-ended, ±12 V levels), not RS-485.
• Protocol: Siemens proprietary serial loader protocol handled by the OP7 bootloader, not PPI.
• Handshake: Hardware handshaking using RTS/CTS and DTR/DSR, which a passive PPI cable does not provide.

Connecting a PPI cable to the OP7 configuration port will not damage the panel, but ProTool / ProSave will time out without establishing a session. Use a null-modem RS-232 serial cable as detailed in the next section.

4. Required Cable Hardware

5. Serial Cable Pinout (PC ↔ OP7 IF1A)

The wiring below implements a complete null-modem configuration with hardware handshaking crossed on both pairs. This is the recommended pinout for reliable ProTool / ProSave loader sessions on the OP7-DP.

Figure 1 — Null-modem cable wiring between PC COM port and OP7 IF1A configuration port.

6. Entering Transfer Mode

The OP7 boots into either normal runtime (if a valid image exists) or transfer mode (if forced by the operator). To force transfer mode for an upload:

1. Power down the panel completely.
2. Locate the two physical keys on the OP7 membrane keypad: ESC (top-left cluster) and the up-arrow (Button up) on the cursor / navigation block.
3. Press and hold both keys simultaneously.
4. While holding the keys, apply 24 V DC to the panel's power terminals.
5. Continue holding for approximately 3 to 5 seconds after the display becomes active.
6. The LCD displays the message "Ready for transfer". Release the keys.

If the panel instead boots to the normal process screen, the keypress was mistimed. Power down, repeat the procedure, and ensure both keys are mechanically engaged before the backlight comes on.

7. ProTool / ProSave Configuration Workflow

Two software paths reach the OP7 configuration port:

Recommended transfer parameters in ProTool under File → Transfer → Settings:

Interface:          Serial (IF1A)
COM port:           COM1 (or the COMx number assigned to the USB-serial adapter)
Baud rate:          38400 bit/s
Data bits:          8
Parity:             Even
Stop bits:          1
Handshake:          RTS/CTS (hardware)
Timeout:            60 s

8. Upload Procedure (Step-by-Step)

1. Build or verify the null-modem serial cable per Section 5.
2. Connect the cable between the PC's COM port and the OP7 IF1A connector.
3. Launch ProTool / ProTool Lite V6.0 SP3.
4. Choose File → Transfer → Upload from device.
5. ProTool prompts for a target folder; choose a directory with full NTFS write permission. The image is typically 512 KB to 1 MB depending on the project size.
6. Force the OP7 into transfer mode using the Section 6 keypress procedure.
7. ProTool displays "Establishing connection"; this can take up to 30 s on the first attempt.
8. When the upload completes, ProTool logs the file as .pwl (ProTool configuration) or a binary .img-equivalent runtime file depending on the OP7 firmware variant.
9. Power-cycle the OP7 to return to runtime, or leave the panel in transfer mode for a subsequent restore operation.

9. Image-File Compatibility Constraints

This is the most misunderstood aspect of the OP7 upload workflow and must be communicated to anyone commissioning the spare panel:

• What is uploaded: A compiled, tokenized runtime image. Variables, screens, alarm logs, and recipes are preserved. Source code, screen layout, and tag names are not readable or editable.
• What is not uploaded: The original .pwl source project. There is no "decompile" path on OP7 firmware.
• Restore target: The image can only be downloaded back to a panel carrying the identical MLFB. In practice this means 6AV3607-1JC20-0AX1 to 6AV3607-1JC20-0AX1. Cross-flashing to a different OP7 variant (e.g. 6AV3607-1JC30-0AX1) is rejected by the bootloader.
• Checksum: The OP7 bootloader verifies a CRC over the image. Any modification, truncation, or sector error during transfer will abort the upload with a "Transfer error" message and the panel remains in transfer mode awaiting a retry.

10. Troubleshooting Matrix

11. Verification Procedure

After a successful upload, validate the image before archiving or restoring:

1. Open the saved image in ProTool under File → Open → Restore device backup. ProTool reports the panel's MLFB and firmware revision; verify both match the source machine's asset record.
2. Compare the file size to a known-good reference (typically 384 KB to 1 MB for OP7 projects). A file truncated below this range indicates a partial transfer.
3. Compute a CRC32 over the saved file and log it on the asset record. This CRC must match the CRC computed on a subsequent re-upload of the same panel.
4. If the spare panel is on hand, perform a restore followed by a manual power-cycle and verify that all configured screens and alarms appear as expected.
5. Reconnect the panel to its target S7 PLC over Profibus and verify that the configured tag polling starts; absence of tag updates indicates the image was corrupted in transfer.

12. Field-Proven Caveats and Best Practices

• Document before you disconnect. Photograph the OP7's Profibus node address, the configured baud rate (visible in the panel's diagnostics menu), and the DP master GSD file version. The uploaded image contains none of this metadata in human-readable form.
• Power supply stability matters. Brown-outs during the upload can corrupt the image and require a re-upload. Power the OP7 from a clean 24 V supply or a UPS during the procedure.
• Prefer ProTool over ProSave when you need to inspect alarms. ProSave is faster for a binary backup, but ProTool presents the tag database and alarm class configuration, which is invaluable when reverse-engineering a legacy project.
• Lock the spare panel's part number. Many OP7 spare panels in stockrooms have been "upgraded" to OP17 or OP27 variants over the years. Always read the MLFB label and confirm 6AV3607-1JC20-0AX1 before attempting a restore.
• Avoid serial ports on docking stations. Internal COM ports on industrial PCs are preferred over USB-serial bridges for production transfers; if a bridge must be used, isolate it electrically and keep cable length under 2 m.

13. Frequently Asked Questions