How to Connect CFC Logic to a PCS 7 Safety Matrix

Use External connection when a cause or effect must connect to an existing signal in the safety program through a CFC chart connection; the Safety Matrix creates a matrix-logic chart pin for that connection. Use Channel driver for fail-safe I/O tags assigned through the project's symbolic F-I/O configuration, and Customer-specific only for a qualifying customer-specific F-channel driver. A tag appearing in the I/O selector is therefore not the same as a generic CFC chart signal.

Applies To and Prerequisites

The discussion identifies the Safety Matrix Engineering Tool as V6.3 in an integrated STEP 7/PCS 7 multiproject, but does not give the update level, PCS 7 version, CFC version, S7 F Systems version, or the kind of “gray logic” signal that the author was trying to connect.

The detailed tag-integration procedure described here is in Siemens' Safety Matrix Configuration Manual, 06/2015, A5E33216084-AB (Safety Matrix V6.2). It documents the External connection, Channel driver, and Customer-specific options and their CFC/F-I/O roles. Siemens' later V6.3 SP1 Readme lists the component versions required for that specific SP1 package and corrections to the Programming and Operating Manual; those requirements must not be assumed for every V6.3 installation. Confirm the installed Safety Matrix, PCS 7, CFC, S7 F Systems, and library versions against their matching documentation before engineering.

The Safety Matrix is for an S7 F/FH safety program. A standard non-safety signal is not made safety-related merely by selecting an External connection. Use only signals and logic permitted by the project's safety design and applicable functional-safety rules.

Choose the Tag Integration Type

Selector optionWhat it representsWhen it fitsExternal connection (#)A signal from the safety program connected through a CFC chart pin. For a cause input, the matrix logic gets a chart input; for an effect output, it gets a chart output.Use when the signal is produced or consumed elsewhere in safety-program CFC logic and should be wired through the matrix chart interface.Channel driverAn input/output tag tied to fail-safe module I/O. The Safety Matrix can create and connect an F-channel driver during transfer when the appropriate SIMATIC F-module driver does not already exist.Use for configured fail-safe I/O represented by project symbolic names.Channel driver – Used externally (@)A channel-driver tag already configured by another Safety Matrix or user logic. During transfer, the matrix links to the existing driver; the tool may add the @ prefix and select Used externally.Use only when the intended F-channel driver already exists and the transfer is to reuse it.Channel driver – Customer-specific (~)A signal from a customer-specific F-channel driver.Use only when the project includes a driver that meets the applicable Safety Matrix customer-specific driver requirements. It is not the general option for an ordinary CFC signal.

These terms are distinct from selecting an intersection. A cause row and an effect column must both be configured before their intersection can be assigned.

Why the Selector Shows Only I/O Tags

The Channel driver path selects inputs and outputs configured as F-I/O in HW Config or the SIMATIC Manager symbol table. Seeing the project's I/O symbols in that picker is expected: those symbols are the matrix interface to the fail-safe modules.

An arbitrary signal produced by CFC logic belongs to the safety-program signal path. Configure that tag as External connection so the matrix exposes its pin, then connect the pin in the generated CFC chart. The selector's I/O list is not a browseable list of all CFC block pins. A tag such as #LSLL3200 uses the number-sign prefix documented for an external chart connection; the ticket does not establish what signal its particular LSLL3200 represented.

Procedure: Add a Cause or Effect Using an External Connection

Confirm that the source or destination is part of the project's approved safety program and that its data type and signal meaning match the intended cause or effect. Do not use an ordinary non-safety CFC signal as a safety input.
In the Safety Matrix cause or effect configuration area, open the relevant cause row or effect column. The Siemens manual describes double-clicking the row or column, or choosing Change cause / Change effect from its context menu.
In the details dialog's Configure tab, use I/O to open the tag integration choices. Choose External connection for a signal that is to be wired through a CFC chart connection. Enter the approved connection name using the syntax supported by the installed CFC/Safety Matrix version. The manual marks these connections with the # prefix; verify the resulting name after entry.
Configure the rest of the cause or effect according to the approved safety requirements. For an effect, select the appropriate fail-safe output and effect behavior; an external chart pin does not replace the required fail-safe output configuration.
Save and transfer the matrix to the PCS 7 project. The transfer generates the matrix logic and its connection interface in CFC. The Safety Matrix V6.2 manual identifies the generated matrix-logic nested chart as @MatrixName; confirm the corresponding generated chart name in the installed tool before wiring.
In CFC, connect the exposed matrix input pin to the approved safety-program signal, or connect the matrix output pin to the intended safety-program logic. Check the signal direction and data type at both ends. Do not modify protected or automatically generated matrix logic outside documented editing points.
Configure the cause/effect intersection only after both sides are defined. Run the matrix validation/reporting and project-specific safety verification before compiling, downloading, or accepting any change.

When to Use a Channel Driver Instead

For an actual fail-safe module input or output, configure the symbolic I/O tag and use the channel-driver integration option. The Safety Matrix manual says it can place F-channel drivers during transfer when they do not already exist for the selected channel. For an already configured driver, the Used externally variation reuses that driver instead of treating the tag as an unconnected ordinary CFC signal.

A customer-specific driver is a separate case. The V6.2 manual reserves Customer-specific for signals from customer-specific F-channel drivers; Siemens' V6.3 documentation includes additional requirements and amendments for that feature. If the picker only offers ordinary project I/O symbols, do not select Customer-specific to force a standard CFC pin into the matrix. Use the External connection path for a supported safety-program chart connection, or have the project's safety-system designer determine the correct driver integration.

Verification

After transfer, inspect the generated CFC chart interface and confirm the # connection has a corresponding pin and intended connection in the right direction. Confirm the signal source belongs to the intended safety program and that the cause/effect configuration and intersection are present in the matrix.

Review the Safety Matrix validation/configuration reports and CFC compile results for missing or incorrect connections. Then follow the project's documented safety-program comparison, function test, and acceptance procedures. A visible tag in the I/O picker, successful transfer, or successful compile alone does not verify the safety function.

Limitations and Operational Precautions

The ticket ends by saying the author obtained the needed information, but it does not preserve the final configuration or say exactly which option resolved the issue. It also does not identify what “gray logic” means in that project. Therefore, this article explains the documented tag categories and connection method without asserting the cause of that specific screen state.

The opened detailed manual is for V6.2; the source states V6.3, and its exact update level is unknown. The V6.3 SP1 Readme is not a substitute for the V6.3 Programming and Operating Manual. Confirm the corresponding version-specific rules and interface before changing a safety matrix. Keep ordinary logic outside the safety function unless the approved design specifically routes an appropriately qualified signal into the F-program. Transfer, compile, download, and test are separate activities; follow the site safety lifecycle and approved change/acceptance process.

Engineer FAQ

Why does the I/O button show only project I/O symbols? The Channel driver option selects F-I/O tags from the configured project symbols. A CFC chart signal uses the External connection option instead.

What does the # prefix mean? In the cited Safety Matrix manual, it labels a chart connection. The matrix exposes an input pin for a cause signal or an output pin for an effect signal in its nested matrix-logic chart.

Does External connection make a standard CFC signal fail-safe? No. It describes how a safety-program signal is connected to the matrix. It does not change the signal's safety classification or validate its source.

What does the @ prefix mean? The manual uses it for a channel driver that already exists elsewhere in the project and is reused by the matrix; the tool identifies this case during transfer.

When should Customer-specific be selected? Only when the signal comes from a customer-specific F-channel driver that conforms to the requirements for the installed Safety Matrix and S7 F Systems versions.

Technical References

Siemens, Safety Matrix, Configuration Manual, 06/2015, A5E33216084-AB. See §§4.1.1–4.1.3 for supported tags, External connection (#), Channel driver, Used externally (@), Customer-specific (~), and tag naming; §§4.3–4.5 for configuring causes, effects, and intersections; §6.1 for transfer to CFC. Open the Siemens manual (PDF)
Siemens, Safety Matrix V6.3 SP1 Readme, 08/2023, A5E51751876-AB. See §§3.1 and 4.5 for package version requirements and version-specific notes/corrections to the Programming and Operating Manual. This source establishes V6.3 SP1 details only. Open the Siemens Readme (PDF)

How to Connect CFC Logic to a PCS 7 Safety Matrix