Specifications

Page 19

FIREFINDER SERIES II INSTALLATION, COMMISSIONING &

OPERATION

4.14 Slave CPU (302-669)

The Slave CPU (Central Processing Unit) provides the interfacing signals and I/O’s required to allow

the FACP to connect / communicate to a variety of termination boards.

A single chip micro controller U1 controls all operations of the FACP Slave CPU. This device

contains the control program within Read Only Memory (ROM).

Communication to the main system is via an eight bit bi-directional bus (CN1). Integrated circuits U5,

U3 and U7 provide buffering and data latches that allow data flow between the Main and Slave

CPU’s. The buffers hold one output byte and two input bytes.

CN1 provides the interconnection to the Termination Board. Within CN1 are ten analogue input lines,

two input/output lines, two current loop outputs (RS422) and one current loop input (RS422).

All analogue inputs are de-coupled then fed to an eight-bit analogue to digital converter (ADC) U4.

The data from the ADC is sent via a serial peripheral interface to the micro controller U1.

The current loop inputs and outputs are used to provide various signals according to the board

connected. The signals provided can be serial peripheral interface clock and data signals or full

duplex asynchronous data and a timing output. U6 provides the signal multiplexing and buffering

required to switch between different functions.

Automatic Termination Board Sensing

A unique feature of the Slave CPU is its ability to automatically sense the type of board it is

connected to without the user having to configure the board to suit. Board sensing is done by

measuring the voltage on analogue input ten (CN1-10), denoted Type Voltage. Each termination

board provides a unique predefined voltage. After the Slave CPU has determined the board type the

Slave CPU will set the appropriate operating conditions, signal the Main CPU of the installed type

and wait for the Main CPU to inform the Slave to begin executing the program.

Connections

CN1

To 302-735 or 302-671 or 302-672 or BRD85DLTB-B

TLC542

CN2

302-696

CN1

Main Board

Figure 23: Slave CPU Board