Siemens CP524-3UA15 and CP524-3UA13 Compatibility in EG 185U Racks

The Siemens SIMATIC S5 CP 524 communication processor was a serial interface module used in S5-115U, S5-135U, and S5-155U programmable logic controllers to provide point-to-point and multi-point serial links to operator panels, printers, scanners, and third-party devices. Two of the most frequently encountered order variants in legacy systems are CP524-3UA13 and CP524-3UA15. This reference consolidates the rack-compatibility question, the jumper configuration procedure, and the supporting COM 525 software configuration that is required when substituting one variant for the other in an EG 185U subrack.

1. CP 524 Module Overview

The CP 524 is a single-channel serial communication processor that occupies one slot in an S5 central or expansion rack. It provides a configurable physical interface (typically RS-232C, RS-422, or RS-485, depending on wiring side), an internal 256-byte dual-port RAM mail buffer, and a loadable protocol driver selected through the COM 525 / COM 527 / COM PACK tooling. The module is intended for asynchronous, character-oriented protocols such as 3964(R), RK 512, and various transparent driver modes used for ASCII terminals and barcode readers.

2. CP524-3UA13 vs CP524-3UA15 — What Is Different

The two order numbers refer to hardware revisions of the same functional module. From a planning and maintenance standpoint the differences fall into three categories:

1. Component population: The 3UA15 board is a later revision using a different gate-array and serial interface IC compared to the 3UA13. The functional interface to the S5 backplane bus is unchanged.
2. Jumper block layout: The on-board jumper for interface selection (RS-232, RS-422, TTY/20 mA current loop, and module address) is physically re-positioned between revisions. The pin header is the same function, but the jumper pins to bridge differ between 3UA13 and 3UA15.
3. Firmware baseline: Later revisions ship with a slightly newer EPROM baseline. Both revisions are loadable with the same protocol driver set; the older EPROM is a subset, not a superset.

3. Rack Compatibility — EG 185U

The EG 185U is a 19-inch subrack with 18 usable slots, used in S5-115U central configurations and in S5-135U/S5-155U expansion frames. Both CP524-3UA13 and CP524-3UA15 are mechanically and electrically compatible with this subrack:

Compatibility considerations for any rack:

• The slot in the EG 185U must be an I/O slot (per the S5 slot numbering scheme) and must not be assigned a different page-frame area. CP 524 occupies a 32-byte input and 32-byte output image.
• The 5 V backplane supply must be confirmed. A CP 524 typically draws ~1.0 A at +5 V; ensure the rack's PSU has margin after the CPU, IM, and any other CPs are accounted for.
• If the EG 185U is loaded into a 24 V environment, the rack's fan/ventilation must be intact. Heat dissipation per slot is low, but a sealed cabinet at 40 °C ambient can still push the electrolytics on older 3UA13 boards out of tolerance.

4. Jumper Configuration on CP524-3UA15

The single most common pitfall when swapping a 3UA13 for a 3UA15 is leaving the factory-default jumper in place. The 3UA15 is shipped with the interface set to RS-232 and the module address at default 0 (or in some cases 255, depending on EPROM mask). The on-board jumpers control four functions:

1. Physical interface selection (RS-232C / RS-422 / TTY 20 mA current loop)
2. Module address (0 to 255 on the S5 backplane page frame)
3. Interface number (logical interface referenced by COM 525 / STEP 5 COM configuration)
4. Termination / fail-safe biasing for RS-485 multi-drop

For the CP524-3UA15 specifically, the jumper block is located near the front-edge 25-pin D-Sub connector, labelled in silk-screen on the PCB. The exact pin pairs to close for each function are documented in the COM 525 manual (Volume 1/2, page 87 and following) and in the Siemens Support FAQ entry "Setting the interface number or module address on the CP 524".

4.1 Standard Jumper Procedure

1. Power down the EG 185U rack and isolate the 24 V / 120 V / 230 V supply to the rack PSU.
2. Remove the CP 524 from its slot and place it on an ESD-safe mat.
3. Identify the jumper pad rows. On the 3UA15 these are typically labelled X1 through X4 (or BR1 through BR4 on early boards).
4. For RS-232C: install jumpers in the RS-232 row. For RS-422: install jumpers in the RS-422 row. For 20 mA current loop (TTY): install jumpers in the TTY row. The 25-pin D-Sub pinout is the standard Siemens assignment, not the IBM PC pinout.
5. For the module address, set the eight address jumpers to the binary value of the desired slot address (0-255). In a single-rack S5-115U configuration, the CPU is normally address 0 and the CP 524 is set to a free address such as 4, 6, or 8.
6. For the interface number, set the four-bit logical interface number. This is the number referenced from the COM 525 protocol parameter assignment block (for example, IF 1 in COM 525 must match the hardware jumper on the CP 524).
7. Re-install the module, power up the rack, and verify with the COM 525 online test.

4.2 Sample Module Address Settings

5. COM 525 Configuration Software

The CP 524 is configured and parameterised using the COM 525 programming package (S5-DOS). COM 525 is a DOS-based parameterisation tool that produces a loadable parameter block written to the CP 524's EPROM or downloaded into the module's RAM through the S5 online interface.

The COM 525 manual, "COM 525 Programming Package for the Communication Processors CP 524 and CP 525 (S5-DOS), Volume 1/2, page 87 and following", contains the definitive interface-number and module-address tables. The relevant Siemens support entry for this document is:

• COM 525 Programming Package for CP 524 and CP 525 (S5-DOS) — Siemens Support ID 15352689

The companion FAQ entry for setting the interface number and module address is:

• Setting the interface number or module address on the CP 524 — Siemens Support ID 10535062

5.1 COM 525 Parameter Block Fields

6. Step-by-Step: Swapping CP524-3UA13 for CP524-3UA15

1. Document the existing configuration. Photograph the jumper block of the 3UA13 before removal. Note the COM 525 parameter block values stored in the EPROM.
2. Power down the rack and apply lockout/tagout to the rack PSU.
3. Remove the 3UA13 and place on an ESD-safe mat. Label the front connector with the wire number to preserve the field wiring.
4. Inspect the 3UA15 for transit damage. Verify the EPROM label matches the driver set required by the application (e.g., RK 512, 3964R).
5. Set the interface jumpers on the 3UA15 to match the physical interface used by the field wiring (RS-232 / RS-422 / TTY).
6. Set the module address jumpers to the same value as the removed 3UA13. If the application used IF 1, set the logical interface number jumper to 1.
7. Re-install the module in the same slot of the EG 185U rack.
8. Power up the rack and observe the CP 524 LEDs. The ST (status) LED should transition from flashing to steady after approximately 2-3 seconds if the module passes self-test.
9. Load the COM 525 parameter block into the CP 524. This step is necessary even though the hardware settings are correct, because the protocol driver and timing parameters are stored in COM 525, not in hardware.
10. Run an end-to-end loopback test with a terminal or PC running the matching protocol. For 3964R, the test should report ACK in response to a STX within the configured acknowledgement time (default 1000 ms).

7. Verification and Commissioning

After the swap is complete, verify the following in sequence:

8. Common Failure Modes and Diagnostics

9. Field-Proven Caveats

• Component drift on old 3UA13 boards: The electrolytic capacitors on the 3UA13 are at the upper end of their service life in many plants. When substituting a 3UA15, do not assume that the field wiring, cable shields, and connector pins are still in good condition. Inspect the 25-pin D-Sub connector on the field side and re-crimp if necessary.
• EPROM version compatibility: A 3UA13 EPROM may not be byte-compatible with a 3UA15. If a working EPROM from a 3UA13 is transferred, the CP 524 may still boot but the protocol driver may misbehave. Always re-burn or re-load the parameter block from a known-good COM 525 project for the 3UA15.
• EG 185U ventilation: When the EG 185U is mounted in a sealed cabinet, both 3UA13 and 3UA15 boards will run hot. The 3UA15 generally runs 3-5 °C cooler at the same load because of the more efficient gate array, but the cabinet airflow must still be verified.
• Mixed CP 524 / CP 525 in the same rack: A CP 525 (3UF5 series) can coexist with a CP 524 in the same EG 185U. The two use different module addresses, and the COM 525 / COM 527 parameter tools are separate, but they share the same bus arbitration.
• Spare inventory: If a plant standardises on 3UA15 for spares, it is acceptable to use a 3UA15 in any slot that previously held a 3UA13. The reverse (3UA13 as a spare for a 3UA15) should be avoided because the jumper block drawing differs and field technicians may mis-set it.

10. Quick Reference Summary

11. Related Documentation

• COM 525 Programming Package for CP 524 and CP 525 (S5-DOS) — Siemens Support ID 15352689
• Setting the interface number or module address on the CP 524 — Siemens Support ID 10535062
• COM 525 manual Volume 1/2, page 87 and following