EMERSONDeltaV SISTM Logic Solver

 World’s first smart SIS Logic Solver

 Integrated, yet separate from the control 

system

 Easy compliance with IEC 61511

 Scales to fit any size application

 SIL 3-rated

 Online addition of Logic Solvers

Introduction

The DeltaV SIS system, part of Emerson’s smart SIS, 

ushers in the next generation of Safety Instrumented 

Systems (SIS). This smart SIS approach uses the power 

of predictive field intelligence to increase the availability of 

the entire safety instrumented function.

Benefits

The World’s first smart SIS. Research shows that 

over 85% of all faults in SIS applications occur in field 

instruments and final control elements. The DeltaV SIS

system has the first smart Logic Solver. It communicates 

with intelligent field devices using the HART protocol to 

diagnose faults before they cause spurious trips. This 

approach increases process availability and reduces 

lifecycle costs.

Integrated yet separate. Safety standards insist on 

separation of the control and safety systems in order to 

remove any possibility of a common failure affecting both 

layers of protection. End users require an integrated 

configuration, maintenance, and operations environment. 

The DeltaV SIS system has a unique solution to this 

problem; implementing safety functions with dedicated 

hardware, software, and networks while being seamlessly 

integrated at the workstations.

Easy Compliance with IEC 61511. IEC 61511 

demands rigorous user management and the DeltaV SIS 

platform provides it. IEC 61511 requires that any changes 

made from an HMI (e.g. to a trip limit) be extensively 

vetted to ensure that the right data is written to the right 

Logic Solver. The DeltaV SIS system automatically 

provides this data verification.

Scales to fit any size application. Whether you have 

an isolated wellhead or a large ESD/fire and gas 

application, the DeltaV SIS system scales to provide you 

with the safety coverage you need for your SIL 1, 2 and 3 

safety functions. Each Logic Solver has dual CPUs and 

sixteen channels of I/O built into it. This means that no 

additional processors will ever be required to expand the 

system, since each Logic Solver contains its own CPUs. 

Scan rate and memory usage are constant and 

independent of system size.

SIL 3-rated. DeltaV SLS 1508 Logic Solvers are installed 

in redundant pairs for increased process availability of 

your SIS loops.

A redundant SLS 1508 Logic Solver

Redundant architecture includes:

 dedicated redundancy link

 separate power supply to each Logic Solver

 I/O published locally every scan on redundant peerto-peer link

 same input data for each Logic Solver

Online addition of Logic Solvers. The system 

checks for new hardware every scan, so equipment can 

be added to an on-line system in real time. Online addition 

of new logic solvers means your process does not get 

interrupted. As new equipment is added, the DeltaV 

Explorer software recognizes it and makes it ready to be 

configured.

Product Description

This section provides general information on DeltaV SIS 

hardware. Refer to the Installing Your DeltaV Digital 

Automation System manual for more information on

DeltaV system equipment.

DeltaV SIS Equipment

A DeltaV automation system consists of carriers, one or 

more I/O subsystems, controllers, power supplies, 

workstations, and a control network.

The DeltaV SIS system consists of:

 Redundant Logic Solvers (SLS 1508) and termination 

blocks

 SISnet Repeaters (see separate product data sheet)

 Carrier extender cables

 Local peer bus extender cables

 Right 1-wide carrier with termination

Logic Solvers (SLS1508) contain the logic-solving 

capability and provide an interface to 16 I/O channels that 

can be configured as Discrete Input, Discrete Output, 

Analog Input (HART) and HART two-state output 

channels. Logic Solvers and termination blocks install on 

the 8-wide carrier. Logic Solvers communicate with each 

other through the carriers over a two-channel, local peer 

bus (SISnet) and remote peer ring. Local Logic Solvers

are hosted by the same DeltaV controller and remote 

Logic Solvers are hosted by a different DeltaV controller. 

Logic Solvers are powered by a 24 V DC power supply 

that is separate from the power supply that drives the 

DeltaV controller and I/O. Logic Solvers install in oddnumbered slots (1,3,5,7) on the 8-wide carrier. Redundant 

Logic Solvers use four slots.

SISnet Repeaters extend communication beyond the 

local Logic Solvers connected to one DeltaV controller and 

broadcast global messages to remote Logic Solvers 

through a fiber-optic ring Carrier extender cables extend 

Local Bus power and signals between 8-wide carriers. 

Local peer bus extender cables extend the local peer bus 

(SISnet) between Logic Solvers on different carriers. 1-

wide carriers with terminators terminate the local peer bus 

at the final carrier.

Communication

Control Network: The DeltaV Control Network provides 

communication between the nodes in the DeltaV network. 

Refer to the Installing Your DeltaV Digital Automation 

System manual for complete information on the Control 

Network.

Local Bus: The Local Bus provides communication 

between DeltaV controllers and Logic Solvers and 

between DeltaV controllers and SISnet Repeaters.

Local Peer Bus (SISnet): Logic Solvers communicate 

with other Logic Solvers and with local SISnet Repeaters 

through the carriers over a 2 channel local peer bus. The 

same message is broadcast over both channels. The local 

peer bus must be terminated at both ends. The local peer 

bus is terminated at the left end through the 2-wide 

power/controller carrier and at the right end through a 

terminated 1-wide carrier.

The SISnet Repeaters can be located anywhere on a local 

peer bus – between the DeltaV Controller(s) and the 

terminated 1-wide carrier.

Remote Peer Ring: SISnet Repeaters hosted by one 

DeltaV controller communicate with SISnet Repeaters 

hosted by a different DeltaV controller over a fiber-optic 

remote peer ring. A local SISnet Repeater collects locally 

generated messages that have been designated as global

variables into a single message and sends it to the next 

SISnet Repeater in the ring. Upon receipt of a message, 

the receiving SISnet Repeater broadcasts it on its local 

peer bus (SISnet) and forwards the message to the next 

SISnet Repeater in the ring. A global message is 

forwarded around the ring once. The primary SISnet 

Repeaters form one fiber-optic ring and the secondary 

form a separate, independent ring.

Carrier extender cables and local peer bus extender 

cables connecting a DeltaV controller and 8-wide carrier 

with standard DeltaV I/O and DeltaV SIS Logic Solvers to 

a second 8-wide carrier (hosted by the same controller) 

are installed with Logic Solvers, SISnet Repeaters, and a 

terminated 1-wide carrier. Logic Solver messages are 

communicated to a remote DeltaV SIS (hosted by a 

separate controller) through fiber-optic cables.

DeltaV SIS Product Data Sheet

May 2013 – Page 5 DeltaV SIS Logic Solver

Unique Redundancy Methodology

Introduction to Redundancy

Unlike other SIS Logic Solvers, the SLS 1508 is rated 

suitable for use in SIL 3 applications in simplex mode. 

Redundant SLS 1508 Logic Solvers run in parallel at all 

times. Both read the inputs from the I/O terminals, both 

execute the logic and both drive the outputs at the I/O 

terminals. There is no concept of primary and backup or 

master and slave, which is unlike any other SIS. The only 

difference between the two is that one communicates with 

both the engineering and operator workstations and the 

dedicated safety network (SISnet); this is the one with the 

Active light on the bezel. The other (Standby) is 

communicating only on the SISnet.

In the event that a failure is detected in one of the SLS 

1508 Logic Solvers, it automatically goes to a failed state. 

In this condition all its output channels are de-energized; 

this has no impact on the other Logic Solver or the 

physical outputs because the other Logic Solver continues 

to read inputs, execute logic and drive outputs. The 

transition from redundant to simplex mode is therefore 

completely bumpless.

Redundancy

The redundant SLS 1508 Logic Solver modules are 

connected to the field at the redundant terminal block. No 

control strategy configuration is required to take 

advantage of SLS 1508 Logic Solver redundancy, as the 

system’s auto-sense capability automatically recognizes 

the redundant pair of Logic Solvers.

An integrity error alarm in a redundant Logic Solver pair 

will notify the operator of a failure. Both Logic Solvers in a 

redundant pair are monitored for integrity alarms at all 

times.

Events that can cause integrity alarms include:

 Hardware failure within a Logic Solver

 Communications failure between a Logic Solver and 

the SISnet

 Communications failure between a redundant pair of 

Logic Solvers

 Communications failure between a Logic Solver and 

an DeltaV Controller

 Removal of a Logic Solver from the carrier

The health and status of both Logic Solvers and their 

channels are available in the diagnostics explorer.

When one of a redundant pair of SLS 1508 Logic Solvers 

is removed online there is no disturbance to the process. 

When the missing Logic Solver is replaced with another 

Logic Solver, the new Logic Solver completes its power-up 

self-tests before the active Logic Solver cross-loads the 

current database. In safe areas, failed Logic Solvers can 

be replaced under power. In hazardous areas, appropriate 

installation procedures must be followed.

Automatic proof testing can be selected on a redundant 

pair of Logic Solvers. The desired proof-test interval is set 

in the configuration and the Logic Solvers perform the 

proof test automatically. A warning is given to the operator 

before the automatic proof test is started.

Sequence of Events Capability

With DeltaV SIS, events are automatically generated as 

function blocks are executed within a module scan. Events 

are time stamped with a resolution of <1 ms, and they are 

recorded in the sequence that they occur in the Event 

Chronicle. When using standard function blocks such as 

input blocks, voter blocks, and cause and effect blocks, a 

standard set of events are automatically generated without 

special configuration or programing required. For example, 

I/O failures, trip limits, first outs, and other similar events 

are automatically time stamped by function blocks and 

recorded in the Event Chronicle. When a process variable 

exceeds the trip limit, DeltaV SIS records the event along 

with the analog value and the trip condition.

In general, when there is a plant event that triggers an 

emergency shutdown from the SIS, one input will exceed 

a trip limit on one scan and this will cause outputs to trip 

and more inputs will then change state. Sequence of 

Events Recording has been used to find that first input that 

caused the trip by looking at all of the inputs in the plant. 

With the DeltaV SIS system, the operator simply filters the 

Event Chronicle for first out trips, and the first-out is clearly 

visible. 

If higher resolution is required for some channels then 

they can be wired to both the DeltaV SIS Logic Solver and 

also to a DeltaV Discrete Input Card for Sequence of 

Events, which provides a resolution of 0.25 ms.

DeltaV SIS Product Data Sheet

May 2013 – Page 6 DeltaV SIS Logic Solver

System Compatibility

DeltaV SLS 1508 Specifications

SLS 1508 Logic Solver Weight, Heat Generation and Power Consumption

Item Specifications:

Redundant Logic Solver

Weight – 1.20 kg

Heat Dissipation – 24 W

Power – 2 A @ 24 V DC + Dig out Field Loads

DeltaV SIS Product Data Sheet

May 2013 – Page 8 DeltaV SIS Logic Solver

Channel Specifications

The Logic Solver provides 16 channels of flexible I/O, meaning that each channel can be configured as an Analog Input 

(HART), HART Two-State Output, Discrete Input, or Discrete Output channel. 

Analog Input Channel Specifications (includes HART)

Item Specifications:

Number of channels 16

Isolation

Each channel is optically isolated from the system 

and factory-tested to 1500 V DC. No channel-tochannel isolation.

Nominal signal span 4 to 20 mA

Full signal range 1 to 24 mA

2-wire transmitter power 15.0 V minimum terminal-to-terminal @ 20 mA; 

current limited to 24 mA max

Safety / diagnostic accuracy 2.0% of span

Resolution 16 bits

Filtering

2-pole, corner frequency 5.68 Hz

-3 dB at 5.68 Hz

-20.0 dB at 40 Hz (half the sample rate)