Migrating to LOGO! 230RCE: Decoding Legacy B## Block Notation

Overview: Replacing a Failed LOGO! With the 230RCE Variant

When a legacy Siemens LOGO! logic module fails and the program file (.lsc, .lpd, or .bin) is no longer recoverable, the engineer is forced to rebuild the application from photographs, hand sketches, or a description of the original behavior. This scenario is common in generator/transfer-switch monitoring, building automation, and small machine control retrofits where the original LOGO! was installed years ago and the program card was never archived.

The replacement target in this article is the LOGO! 230RCE (Siemens part number 6ED1052-1FB08-0BA0), an 8-digital-input / 4-relay-output variant of the LOGO! 8 family with 400 programmable function blocks, an Ethernet RJ45 port, and a microSD slot. It is a direct functional replacement for the older LOGO! 6/7 generation 230V modules (for example 6ED1052-1MD00-0BA3 or 6ED1052-1FB00-0BA1), but it is programmed in the FBD/UDF/LAD editor of LOGO! Soft Comfort V8.4 or later.

The single most confusing artifact when reading a photo of an old LOGO! 230RCE running ladder-style logic is the B## reference. In legacy programs, B01, B02, B03 are not digital inputs. They are internal function block identifiers that the LOGO! firmware assigned to the AND, OR, latching relay, timer, counter, or special function block the user placed in the schematic. This article explains how to map those references into the Soft Comfort FBD canvas and provides a complete reconstructed program for a utility/generator monitor feeding an Omnitronix SNMP manager.

Understanding the Legacy "B##" Block Notation

The legacy LOGO! programming environment (LOGO!Soft versions 1.x through 5.x) and the on-board editor of the LOGO! 230R (BA0 generation) display each function block with a fixed numerical index. The index is not a user label; it is a runtime slot number assigned by the firmware as the program is compiled.

Three notation conventions appear in old documentation and on the LOGO! integrated display:

• I## – physical digital inputs, e.g. I01, I02, I03 correspond to the screw terminals on the base module. On the 230RCE, these are I1 through I8 (with I1-I4 also accepting 0-10 V analog via 6ED1052-1FB08-0BA0 hardware revision).
• Q## – physical relay outputs, e.g. Q1, Q2, Q3, Q4 on the 230RCE correspond to the four normally-open relay contacts rated 10 A at 240 V AC / 30 V DC.
• B## – internal function block instance number. B01 is the first block the compiler places, B02 the second, and so on. It may be an AND, OR, NAND, NOR, XOR, NOT, latching relay (RS), pulse relay, on-delay, off-delay, weekly timer, counter, threshold trigger, analog comparator, or any other primitive from the LOGO! function library.

When a screenshot shows B01 wired to Q1, the engineer must determine what logic function B01 actually performs. That determination comes from one of three sources: the original program file (if recoverable from a microSD card or a backup), a paper printout of the FBD, or a close-up photograph of the block symbol showing the function glyph (the AND gate icon, the OR gate icon, the bistable relay symbol, etc.). Without one of those three sources, the block type must be inferred from terminal behavior.

LOGO! 230RCE Hardware Specifications

The 6ED1052-1FB08-0BA0 module is the 230 V AC powered, relay-output, Ethernet-equipped variant of the LOGO! 8 generation. Key parameters relevant to a generator/utility monitor retrofit are summarized below.

Full datasheet and ordering information are available in the Siemens Industry Online Support portal at the LOGO! 230RCE product page. The complete SIMATIC LOGO! Manual covers wiring, function block library, and commissioning.

Prerequisites for the Migration

Before opening Soft Comfort and re-drawing the program, gather the following artifacts and confirm the following tools are available.

1. LOGO! Soft Comfort V8.4 SP1 or later installed on a Windows 10/11 PC. The LSC project file extension for LOGO! 8 is .lsc.
2. Ethernet cable (Cat5e or better) for connecting the PC to the 230RCE RJ45 port. The 230RCE ships with DHCP client enabled and a default fallback IP of 169.254.1.1 / 255.255.0.0 when no DHCP server is reachable.
3. Photographs of the original LOGO! front panel showing the LCD with the active program blocks, plus close-ups of the wiring terminals.
4. Original wiring diagram showing which conductor lands on which screw terminal (L1, N, I1, I2, I3, I4, I5, I6, I7, I8, Q1, Q2, Q3, Q4, PE).
5. Siemens microSD card (6ED1057-1AA00-0BA0) or a third-party industrial-grade microSD if the program must be transferred without a PC.
6. Omnitronix SNMP Manager IP address, community string, and MIB/OID mapping for each monitored status point.

Step-by-Step: Translating B## Blocks to Soft Comfort FBD

The migration procedure converts a photograph of the old LOGO! running into an editable, well-documented FBD project on the 230RCE. Perform the steps in the order shown; each step depends on the previous one.

Step 1 - Identify the I/O Inventory From the Photograph

Decode the physical I/O first because the B## blocks reference them.

• I01 = I1 on 230RCE – utility power sense (typically a 115/230 V AC signal from a line-voltage monitor relay or a 24 V DC contact from an ATS controller).
• I02 = I2 on 230RCE – transfer switch position sense (CLOSED on utility, CLOSED on generator, or NEUTRAL).
• I03 = I3 on 230RCE – generator power sense (line-voltage monitor or generator run contact).

The remaining inputs I4-I8 are available for future expansion. On the legacy 230R module (0BA1/0BA3) only 6 digital inputs were standard; the 230RCE provides 8 with no extra wiring.

Step 2 - Decode Each B## Block in the Screenshot

For each B## reference visible in the photograph, classify the block type using the symbol and the inputs feeding it. The most common blocks in a generator monitor are listed below with their Soft Comfort FBD equivalent.

When the block type cannot be determined from the symbol alone, count the connectors entering the block from the left. Two to four inputs imply AND, OR, NAND, NOR, or XOR. One input implies NOT, on-delay, off-delay, pulse, or edge-triggered counter. Three inputs with one marked "S" and one marked "R" is a latching relay.

Step 3 - Reconstruct the FBD in Soft Comfort

1. Open LOGO! Soft Comfort, click File → New, and select LOGO! 230RCE (6ED1052-1FB08-0BA0) as the target device in the bottom-left toolbar.
2. Drag three Digital Inputs from the toolbar onto the FBD canvas. Label them I1 Utility Sense, I2 Transfer Switch Position, I3 Generator Sense.
3. From the GF (General Functions) palette, drop an AND block, an OR block, a NOT block, and an RS latching relay. Wire I1 and I2 into the AND; wire the AND output and I3 into the OR. The OR output becomes the "AC Source Live" bus that drives the SNMP manager output Q1.
4. Drop an On-delay (TON) with parameter Ta = 3 s on the I1 line to debounce the utility-voltage-sense relay. A 3-second delay prevents a brief voltage dip from triggering a false "utility loss" SNMP trap.
5. Drop an Off-delay (TOF) with parameter Tb = 30 s on the I3 line to hold the "generator running" status for 30 seconds after the run contact opens, matching typical engine cool-down timing.
6. Drag four Digital Outputs to the canvas and label them Q1 SourceLive, Q2 OnUtility, Q3 OnGenerator, Q4 GeneratorFault. Wire as shown in the topology below.

Step 4 - Topology of the Reconstructed Program

The signal flow for the generator/utility monitor is shown below. The FBD in Soft Comfort is drawn top-to-bottom; physical inputs enter from the left, internal logic occupies the middle, and relay outputs exit to the right.

Step 5 - Save, Download, and Verify

1. Save the project as GenUtilityMonitor.lsc in the Soft Comfort project directory.
2. Click Tools → Transfer → PC → LOGO!. In the connection dialog, select Ethernet and enter the 230RCE IP address (or accept the default 169.254.1.1 for a direct crossover connection).
3. Click Test to confirm the PC can reach the LOGO! 230RCE. A green status indicator confirms that the LOGO! has responded to an ARP/ICMP probe and the LOGO! Soft Comfort identification frame.
4. Click Download. The 230RCE restarts automatically with the new program; the on-board display shows the LOGO! welcome screen and the Ethernet activity LEDs blink during the restart sequence.
5. Use the cursor keys on the front of the 230RCE to navigate to LOGO! → Program → Start if the module does not auto-run after download.

Wiring the 230RCE Terminals

The 230RCE wiring diagram below reflects the same screw-terminal layout as the legacy 230R module, so a rewire to the same field conductors is possible without disturbing the upstream breakers.

Mapping Q1-Q4 to the Omnitronix SNMP Manager

The Omnitronix SNMP manager expects a digital input per monitored point. Two integration methods are supported: dry-contact wiring into the manager's physical DI terminals, or Modbus TCP polling of the LOGO! holding registers. The physical contact method is preferred when the manager is already installed in the field cabinet and cannot accept a network firmware update.

For the Modbus TCP method, configure the LOGO! 230RCE Modbus TCP server as follows in Soft Comfort:

1. Open Tools → Parameter VM Mapping and assign Q1 to Modbus address 0001, Q2 to 0002, Q3 to 0003, Q4 to 0004.
2. Enable the Modbus TCP server in File → Properties → Ethernet. The default port is 502. Allow at least one connection slot for the SNMP manager.
3. On the Omnitronix manager, create four Modbus TCP polls with function code 01 (Read Coils) starting at register 0, count 4, polling interval 10 s.
4. Map the polled bits to SNMP OIDs in the manager's MIB editor: bit 0 → .1.3.6.1.4.1.XXXX.1.0 (Source Live), bit 1 → OID +1 (On Utility), bit 2 → OID +2 (On Generator), bit 3 → OID +3 (Generator Fault).

For the dry-contact method, the wiring is direct: each relay contact (Q1-Q4) closes to its respective SNMP manager DI terminal, with the manager's internal excitation voltage (typically 12 V DC) supplied by the manager itself. A resistor (1 kΩ, 0.25 W) across each DI prevents false triggering from induced EMI on long cable runs.

Commissioning and Verification

After the program is downloaded and the wiring is complete, perform the following verification steps in order. Record each reading for the as-built documentation.

1. Power-up self-test: Apply 115/230 V AC to L1/N. The 230RCE display should show the LOGO! splash screen for 2 seconds, then enter the message-display mode. The Ethernet link LED on the RJ45 connector should be solid green when the cable is connected.
2. Input simulation: With the main breaker OFF, use a clip lead to jumper I1 to L1. The LOGO! should display I1 = 1. Repeat for I2 and I3.
3. Output test: With I1 jumpered to L1 and I2 floating, the front-panel display should show Q2 = 1 after the 3-second on-delay. Use a multimeter on the Q2 contact to confirm continuity.
4. End-to-end test: Have the Omnitronix manager operator force a poll of Modbus registers 1-4. The manager should report the same state shown on the LOGO! display.
5. Failure-mode test: Disconnect the I1 wire. After 3 seconds, the LOGO! should clear Q1 and Q2, and assert Q3 only if the generator is running (verified by jumpering I3 to L1). If the generator is not running, all four outputs should return to 0.

Troubleshooting Common Migration Issues

Long-Term Maintenance Recommendations

Once the 230RCE is in service, follow these practices to prevent a repeat of the original failure scenario.

• MicroSD backup: Insert a Siemens 6ED1057-1AA00-0BA0 microSD card before energizing. Press ESC → Card → Copy LOGO → to Card on the front panel. The card stores both the program and the parameter set; removing it provides a hot spare.
• LSC archive: Save the Soft Comfort project to a versioned network share. Add a comment header in the FBD documenting the original LOGO! part number and the B##-to-block-type mapping that was applied during migration.
• Firmware pinning: Record the LOGO! 230RCE firmware version in the as-built documentation. The latest stable release as of the LOGO! 8.4 generation is firmware 8.4.01; upgrades should be tested on a bench unit before being pushed to the field.
• Annual inspection: Verify the CR2032 battery status once per year. The 230RCE displays a "Battery" warning icon when the cell voltage drops below 2.4 V; replace within 30 days to preserve the real-time clock for the weekly-timer blocks.

FAQ