Siemens CP 524 Backup with COM 525: Cable and EPROM Guide

Overview

The Siemens CP 524 and CP 525 are communication processors for the SIMATIC S5 family, typically deployed for point-to-point serial links, ASCII/3964(R) protocols, and operator interface tasks. Because both modules are now long-discontinued, the only practical backup strategy is a bit-true copy of the on-board EPROM (or external memory submodule) using an EPROM programmer and the original COM 525 development environment, supplemented by STEP 5 for source preservation.

This reference documents the cable types required to read/write the EPROM, the software environment for COM 525, the practical compatibility limits of the toolchain under modern Windows, and the recommended archive workflow that avoids corrupting the live CP 524 firmware image.

System Identification

Before any backup procedure, confirm the exact variant you are handling. Both CP 524 and CP 525 share the COM 525 software front-end, but they differ in firmware, EPROM layout, and front connector assignments.

The CP 5430 TF in particular is often confused with a general-purpose comms module: its TF suffix denotes Technological Functions (e.g., axis positioning, cam control) on top of the SINEC transport layer. Knowing which module you have prevents you from reading the wrong EPROM with the wrong programmer adapter.

Backup Strategy: Why EPROM, Not Hard Disk

The CP 524/525 firmware and configuration blocks (KD/KS/KB system data blocks) are designed to be loaded into a UV-erasable EPROM (typically 27C256 / 27C512, depending on revision). The COM 525 development package writes the merged result into an EPROM that is then either:

1. Plugged directly into the CP's memory submodule socket, or
2. Burned into a separate plug-in submodule and inserted in place of the original.

A file-level backup on a PC only preserves the source code (.ST, .S5D) — it does not capture the final compiled image with the live protocol stacks, character tables, and CP-internal block layout. To recover a bricked CP, you need the EPROM image, which is why a PROM programmer is part of the required toolchain, not optional.

Required Hardware Toolchain

The PG-to-CP cable is not the same as the EPROM programmer cable. The PG cable connects to the CP's front serial port and operates at protocol level (online programming). The EPROM programmer connects to the chip itself after physical extraction. Both are required for a complete backup.

Cable Pinouts (Per COM 525 Manual)

The COM 525 Programming Package manual (Volume 1/2) documents every supported cable variant with full pinouts and Siemens order numbers. The three primary cable families are:

1. PG ↔ CP 524/525 Online Cable (TTY, 15-pin)

2. PG ↔ CP 524/525 Online Cable (RS-232, 25-pin to 15-pin)

3. CP 524/525 ↔ External Device Cable (per application)

This cable is application-specific. COM 525 manuals list standard cables for printers (COM1, COM2 with XON/XOFF), operator panels, and barcode readers. Always cross-check the protocol mode (ASCII transparent vs. 3964R) — 3964R requires additional handshake wiring that ASCII transparent does not.

COM 525 Software Environment

COM 525 is the dedicated configuration and online tool for CP 524 and CP 525. It is a STEP 5 add-on package and cannot run as a standalone executable — it depends on the STEP 5 framework (DOS, Windows 3.1, or STEP 5 for Windows) for its runtime environment.

Compatibility Matrix

Installation Order

1. Install STEP 5 first (v6.x or v7.23).
2. Insert the COM 525 diskettes and run the installer from within STEP 5.
3. Verify the COM525.INI is created in the STEP 5 project directory.
4. Add the COM 525 paths to STEP5.INI under [packages].
5. Restart the STEP 5 Manager; the COM 525 package appears under Packages.

Windows XP SP2 — Practical Field Notes

The field report contains conflicting claims: one user reports STEP 5 v7.23 starts and COM 525 menus are reachable on Windows XP SP2, while another flatly states "COM 525 will not run on WinXP." The likely truth is in between — the program launches and configuration files can be edited offline, but the DOS-extender memory model and direct port I/O to the PG serial port may fail on real hardware. Treat XP SP2 as archive-only unless you have verified online CP communication on the same image.

Backup Procedure (Step-by-Step)

Phase 1 — Source Preservation (PC-Side)

1. Connect PG to the CP 524 front serial port using the correct cable per the COM 525 manual.
2. Start STEP 5 + COM 525 on the PG.
3. Open Online → PLC → Read Out All Blocks to pull FB, PB, SB, OB, DB, and the COM 525 system data blocks (KD/KS/KB).
4. Save the project as S5BACKUP.S5D on two independent media.
5. From the COM 525 menu, export the CP-specific Communication Configuration to a printable PDF / PRT file and archive it.

Phase 2 — EPROM Image Capture

1. Power down the S5 rack. Wait at least 30 seconds for capacitor discharge.
2. Remove the CP 524 from the rack. Place it on an ESD-safe mat.
3. Locate the EPROM submodule (or on-board EPROM socket, depending on revision).
4. Extract the EPROM using a proper PLCC/DIP extraction tool — never pry with a screwdriver.
5. Place the EPROM in the programmer. Read the device at the correct voltage (Vpp = 12.5 V for 27C256, 12.75 V for 27C512; Vcc = 5 V).
6. Save the binary as CP524__.bin.
7. Compute a SHA-256 checksum and record it in the backup log.
8. UV-erase a verified blank EPROM. Program it from the .bin and verify byte-for-byte.
9. Insert the spare EPROM into a clean submodule housing. Label with date and source CP serial.

Phase 3 — Verification

1. Insert the spare EPROM into a known-good donor CP 524 (or the original, if you can power it in a test rack).
2. Power the rack. Observe the CP's status LEDs — normal sequence is STOP → RUN with the COM LED indicating the configured interface state.
3. Run Online → PLC → Compare Blocks in COM 525 against the S5BACKUP.S5D file. Result must be identical.
4. From a terminal on the CP's serial line, send a test message and confirm the configured protocol (e.g., 3964R handshake completes with STX / ACK / ETX).
5. Document the SHA-256 of the verified spare EPROM in the plant's asset register.

Troubleshooting Matrix

Edge Cases and Field-Proven Caveats

• Submodule vs. on-board EPROM: Some CP 524 revisions integrate the EPROM directly on the PCB. There is no submodule to swap — you must desolder or use an in-circuit programmer. Confirm before ordering spares.
• CP 5430 TF confusion: The TF suffix means Technological Functions, not "transport format." Do not use the COM 525 manual for the CP 5430 TF — it requires a different toolchain (COM 5430 TF / SINEC).
• Battery-backed RAM blocks: DBs in the CP's internal RAM (battery-backed) are not captured by EPROM backup. Document and manually export these separately, otherwise runtime data such as message counts or positioning tables will be lost.
• Checksum regions: The CP's EPROM layout includes a Siemens-specific checksum at the end of the image. Do not edit the binary; let the programmer regenerate it. Manual edits cause boot failures.
• Archive media: EPROMs lose data over decades. Re-read verified spares every 5 years and reburn if needed.

Commissioning Verification Checklist

1. Source project .S5D archived on at least two independent media.
2. Configuration printout archived (paper + scanned PDF).
3. Original EPROM image .bin archived with SHA-256.
4. Spare EPROM programmed and byte-verified.
5. Spare EPROM verified in a donor CP with identical online block compare.
6. End-to-end protocol test message sent and acknowledged.
7. Asset register updated with backup location, media ID, and SHA-256.