Migrating from Obsolete RED_LIB to the Redundant IO CGP Library in SIMATIC PCS 7

In SIMATIC PCS 7 (V8.1 / V9.0 / V9.1), the legacy 'RED_LIB' (V1/V2/V3/V4) software redundancy library used in older releases like PCS 7 V5.x–V7.1 is completely obsolete and unavailable. In modern PCS 7 architectures with S7-400H or CPU 410-5H controllers, redundant I/O channel passivation, monitoring, and depassivation are handled automatically by the 'Redundant IO CGP' (Channel Driver for S7-400H) component integrated natively into the standard PCS 7 Basis Library. Engineers no longer need standalone RED_LIB function blocks; configuring redundant I/O modules in HW Config and compiling CFC charts with 'Generate module drivers' automatically instantiates modern redundant driver blocks.

Executive Summary

During plant revamps and migrations from legacy systems (such as PCS 7 V5.x, V6.x, or V7.x) to modern releases (PCS 7 V8.1, V9.0, or V9.1), engineers maintaining redundant I/O configurations often search for the historic library package RED_LIB (V1) or REDlib V3/V4. In early PCS 7 versions, programming redundant I/O—such as redundant digital input or analog output modules—required manually inserting specialized blocks from RED_LIB to arbitrate channel discrepancies and handle depassivation.

Searching for RED_LIB in modern PCS 7 media yields no results because Siemens declared RED_LIB obsolete starting in PCS 7 V8.0. The entire redundant I/O management framework was redesigned into the Redundant IO CGP (Channel Driver for S7-400H) architecture and embedded directly into the PCS 7 Basis Library. Modern PCS 7 projects manage redundant I/O automatically at compile time without requiring manual redundancy blocks. This guide clarifies the obsolescence of RED_LIB and explains how redundant I/O is configured and managed in modern PCS 7 releases.

Architecture and Fundamental Mechanics

The evolution of redundant I/O handling in SIMATIC PCS 7 reflects a transition from manual programming to automated driver generation:

The Legacy RED_LIB Paradigm (PCS 7 V5.x–V7.1):
- In legacy systems, redundant I/O modules required inserting custom function blocks (RED_IN, RED_OUT, RED_DI) directly into CFC charts.
- Engineers had to manually manage discrepancy timers, passivation bits, and depassivation triggers.
- RED_LIB V1 and V2 supported early software redundancy; REDlib V3 and V4 supported basic hardware redundancy in V7.x.
The Modern Redundant IO CGP Architecture (PCS 7 V8.0+):
- Starting in PCS 7 V8.0 / V8.1, Siemens replaced RED_LIB with the 'Redundant IO CGP' (Channel Driver Generation Package, e.g., V5.2 in V8.1, V5.3 in V9.0, V5.4 in V9.1).
- Redundant I/O is configured purely in STEP 7 HW Config: an engineer selects two identical modules in an ET 200M or ET 200SP HA rack and checks 'Redundant module pair'.
- During CFC compilation, the driver generator (Generate module drivers) scans the hardware redundancy pair and automatically instantiates modern Basis Library driver blocks (such as MOD_D16_R, CH_DI, CH_AI, Pcs7DiIn).
Automated Depassivation and Diagnostic Integration:
- Modern redundant drivers continuously compare signals from both modules. If a discrepancy or channel fault occurs, the driver passivates the bad channel, routes valid data from the partner module to the technological block (e.g., MotL), and triggers diagnostic alarms in WinCC Maintenance Station.
- When the hardware fault is cleared, the system depassivates the channel automatically or via standard operator faceplate commands, eliminating manual block logic entirely.

Step-by-Step Implementation Procedure

Follow these steps to configure redundant I/O in modern PCS 7 without legacy RED_LIB blocks:

Configure Redundant I/O Modules in HW Config:
- Open HW Config for the automation station.
- In an ET 200M or ET 200SP HA rack, insert the primary I/O module (e.g., 16-channel DI module in Slot 4).
- Insert an identical I/O module in an adjacent slot (e.g., Slot 5).
- Right-click the primary module > select 'Object Properties' > switch to the 'Redundancy' tab.
- Check 'Redundant to module' and select the partner module in Slot 5.
- Configure discrepancy times (e.g., 20 ms) and save/compile HW Config.
Assign Symbolic Names to the Primary Module:
- In HW Config, right-click the primary module addresses and open 'Edit Symbols...'.
- Assign clear symbolic names (e.g., Pump101_Run_Feedback).
- Note: Symbols are assigned ONLY to the primary module; HW Config automatically mirrors redundancy to the partner module.
Interconnect Channel Drivers in CFC:
- Open the target CFC chart.
- From the PCS 7 APL Library, insert a standard channel block (e.g., Pcs7DiIn FB1865).
- Connect pin PV_In to the symbolic name Pump101_Run_Feedback.
- Do NOT insert any legacy RED_LIB blocks!
Execute CFC Compilation with Module Drivers:
- Select 'Chart > Compile > Charts as Program...'.
- Select 'Entire program' and verify that 'Generate module drivers' is CHECKED.
- The compiler detects the hardware redundancy pair and automatically builds redundant diagnostic blocks in @ system charts.
Download to Controller and Test:
- Download the program to S7-400H / CPU 410-5H.
- Verify that process signals modulate normally.

Verification

In CFC Test Mode (Online), monitor Pcs7DiIn: confirm that the block receives process signals with Quality Code 16#80 (Good).
Simulate a wire break or pull the field connector on Module 1: confirm that Pcs7DiIn seamlessly switches to Module 2 without signal interruption.
Verify in WinCC Maintenance Station: confirm that a maintenance alarm is logged reporting 'Channel discrepancy / passivation on redundant module pair'.
Reconnect the wire: confirm that the channel depassivates automatically and returns to dual-redundant health.

Limitations and Operational Precautions

Do not attempt to copy legacy RED_LIB blocks from old V7.x archives into PCS 7 V8.1/V9.x projects; mixing obsolete RED_LIB blocks with modern Basis Library channel drivers will cause severe compiler conflicts. Redundant I/O modules must be identical in part number, hardware revision, and firmware. Hardware modules and redundant licensing options should be verified through an authorized Siemens distributor or the Siemens Industry Mall.

Engineer FAQ

Where can I download RED_LIB (V1) for PCS 7 V8.1?

RED_LIB is obsolete and no longer available; redundant I/O in PCS 7 V8.1 and higher is managed by the Redundant IO CGP component inside the PCS 7 Basis Library.