FOXBORO Compact FBM240. Redundant with Readback, Discrete

Compact FBM240. Redundant with Readback, Discrete

Output and Discrete Input Module

Overview

The Compact FBM240is an 8 channel input and 8 channel output Foxboro™ DCS

Fieldbus Module (FBM) available as a single or redundant module. A redundant pair

of the modules combine to provide redundancy at the FBM level, with field I/O wired to

one commontermination assembly (see Figure 1). Each module independently holds

the output(s) at its specified output value(s), and each independently reads back its

observed value of the output.

This module is part of the Compact 200 Series I/O subsystem described in Compact

200 Series I/O Subsystem Overview (PSS 41H-2COV).

Aredundant contact output block in the control software validates each output in

conjunction with information to/from the module.

Features

• Eight discrete outputs/Eight discrete voltage monitor inputs

• Eight discrete inputs read back the voltage across the relay contacts. Sets the

channel BAD if the state of the contact disagrees with the state of the

corresponding output channel

• Monitors each FBMoutput and sets the output channel BAD if the output is in the

wrong state

• Single or redundant module

• Termination Assemblies (TAs) for locally or remotely connecting field wiring to the

Compact FBM240

• Supports discrete relay outputs capable of switching:

◦ 10Aat80to120VAC,or

◦ 5Aat80to125VDC,or

◦ 5Aat15to30VDC,or

◦ 5Aat80to120VAC

• Supports channel-isolated discrete I/O:

◦ 15-60VDC@2A,fusedoutputs

◦ 15-60VDCinputs

FBM240

NOTE: Support for this termination assembly and the new Fail-Safe

configuration options described in Fail-Safe, page 6 require version 1.40N or

later firmware.

• Redundantoperation failure detection

◦ Outputcontact monitor readback and high coverage of internal FBM detected

failures allows redundant partner to automatically continue to drive discrete

outputs and to monitor inputs

• Internal per channel output demand state failure detection

◦ OutputChannel is marked BAD in both Single and Redundant Operation if the

demand state read-back indicates a state of miss-compare

Internal Readback of Output

The Compact FBM240has8internal readback channels, one per each output

channel, used to verify that the output has changed to the requested state. These

channels read the voltage across the relay contacts on the relay termination

assemblies. The states of these channels are displayed on LEDs on the front panel of

the Compact FBM240. When external power is applied to the relay contact of each

channel, the LED for that channel is ON when the relay contact is CLOSED, and OFF

when the relay contact is OPEN. If the state of the contact disagrees with the state of

the corresponding output channel, the channel is marked BAD.

The FBMalso monitors each of its eight outputs and sets the corresponding output

channel BAD if the output is in the wrong state.

If the channel or input power is marked BAD, the CP presents that information to the

Foxboro DCS for display as a System Management alarm and as a control block

alarm

Redundant Outputs

Aredundant contact output function block, COUTR, is used for each redundant pair of

outputs. The COUTR block handles output writes and initialization logic for the

redundant channels. On each write of the COUTR block, identical output writes are

sent to both modules, fully exercising the Fieldbus and the logic circuitry of each

module. You can select a sustained output that follows the block input or a pulsed

output with a selectable pulse width.

Whenafailure is detected in one of the modules, its output is marked BAD and the

corresponding channel in the good module automatically continues to drive the

discrete outputs.