Category: A-B

Temperature Control Using a BTM Module in an SLC System

The temperature control module is an intelligent I/O module that can 

provide a maximum of 4 PID loops for temperature control. The 

module has 4 analog thermocouple (TC) inputs. Each analog input 

functions as the process variable (PV) for a PID loop. The PID 

algorithm and tuning–assisted–process (TAP) algorithm are performed 

on the module for each of the loops. The control–variable (CV) 

output of each loop, either analog output or time–proportioned 

output (TPO), is sent from the module to the SLC data table. Your 

application ladder logic must access the CV value in the data table and 

send the analog or TPO data to an output module to close the loop.

Features of the Temperature Control Module

The 1746–BTM module provides:

• 4 independent temperature control loops

• autotune PID loops (one loop or any combination of loops can 

be autotuned while other loops are running)

• a unique start–up algorithm to minimize overshoot

• an isolated thermocouple (J and K) input for each PID loop

• 16–bit analog–to–digital converter resolution (0.1° resolution)

• a heat CV signal (for each PID loop) as a numeric % value

• a cool CV signal (for each PID loop) as a numeric % value

• a heat CV signal (for each PID loop) as a TPO bit

• a cool CV signal (for each PID loop) as a TPO bit

• temperature values in C ° or F °

• self–calibration (external reference required)

• user–selectable high and low alarms with dead band for hysteresis

• input open–circuit detection

The 1746-BTM module is compatible with any SLC processor that 

supports M0/M1 files, such as the SLC 5/05, SLC 5/04, SLC 5/03, and 

SLC 5/02 controllers.

Vocabulary

In this manual, we refer to:

• the barrel temperature control module as the “1746-BTM 

module,” the “BTM module,” or as “the module”

• the programmable controller as the “SLC processor”, or “the processor”

• a thermocouple as a “TC”

• a time-proportioned output as “TPO”

• the tuning-assisted processes as “TAP”

• proportional-integral-derivative as “PID”

• cold-junction compensation as “CJC”

Current CV

Your ladder logic should read the numeric value (current CV), scale it, 

and send it to an analog output module to generate the control signal 

to an analog temperature control actuator. If using the sample 

program look for current CVs in N10:208–211 for loops 1–4. 

TPO

The module returns the heat TPO (bit 6) and cool TPO (bit 7) in input 

image table words 8–11 for loops 1–4. The sample program sends 

TPO signals to a digital output module to generate the control signal 

to a digital temperature control actuator.

M0 File

contains four axis control structures and five setpoint profiles. 

Each axis has a variety of PID and profiling options, controlled 

by its axis control structure. Each axis also has a unique 

256-point setpoint profile. A single master setpoint profile is used 

with an “interpolate” command to ease the task of generating setpoint profiles. 

Entries in the M0 File are written by move or copy instructions in 

ladder program. Unlike changes made to the Output File, which 

are automatically detected by the module, the module must be 

explicitly instructed to download axis-control structures and 

setpoint profiles from shared memory (done by setting bits in the Output File).

M1 File 

contains four axis-status structures, four process-variable profiles, 

and a single interpolated profile. Axis-status structures are copies 

of respective axis-control structures, except that status 

information has been inserted by the module. Each 

process-variable profile provides a record of the actual position 

response to a setpoint profile. The interpolated profile is the 

result of either a linear or natural cubic-spline interpolation 

performed between the setpoints specified in the master setpoint profile. 

Unlike the Input File, which is automatically updated, the 

module must be explicitly instructed to upload axis-status 

structures, process variable profiles, and the interpolated profile 

to shared memory (done by setting bits in the Output File). 

Entries in this file are then read by move or copy instructions in ladder program.

Output File

contains 32 16-bit entries used by ladder program to command 

module operation. The Output File may also be used to supply 

process data to the module in certain situations. Entries in this 

file are updated automatically, at the end of each scan, by the 

SLC processor from the user data file but may be written at any 

time by immediate I/O instructions in the ladder program.

Input File

contains 32 16-bit entries used by ladder program to extract 

status information from the module. The Input File contains 

acknowledge bits corresponding to control bits in the Output 

File, as well as information pertaining to the profile executing on 

each analog I/O channel (step number, setpoint, analog input, 

process variable, control output, etc.) and a parameter error flag. 

The entries in this file are read automatically, once per scan, by 

the SLC processor into the user data file, but may be read at any 

time by immediate I/O instructions in ladder program.

Overview

The module performs its servo control task independently, but is dependent on the 

SLC processor for all of its configuration and run-time information. The processor 

may be also be used to supply process data or timing information over the 

backplane in certain situations (e.g. parison drop synchronization on continuous 

extrusion machines, or accumulator position in reciprocating screw machines).

The module uses a digital signal processor running a 

Proportional-Integral-Derivative (PID) algorithm to control four axes of motion. 

Four analog inputs and four analog outputs are used for process variables and 

signals, while four digital inputs and four digital outputs are used for start-of-drop 

synchronization and profile step synchronization signals, respectively. An excitation 

voltage is provided for use with linear potentiometers.

Communication with the SLC Processor

• shared memory

• control bit/status bit handshake

• micro processor

• PID control algorithm

• digital I/O

• analog I/O

Features

This 4-axis position-control module has these features:

• Open-loop or closed-loop control

• Independent and coordinated axis control

• Position- and time-based control

• Accumulator push-out control

• Zero-scale/full-scale (offset & span) calibration for position inputs

• PID with anti-windup, bumpless parameter changes, setpoint weighting, and 

limited high-frequency derivative gain.

• Profile interpolation (linear or cubic spline) between setpoints

• Converging/diverging tooling (direct/reverse acting control)

• Three hold values per axis: manual position, purge, or die gap

• Independent profile scale and offset adjustments 

• Automatic parison weight adjustment

• Setpoint marking

Shared memory

From the ladder programmer’s perspective, communication with the module is via 

five data files located in shared memory on the module:

Config(G) File

contains information regarding the operational mode and feature 

settings of the module. You specify the contents of this file with 

the ladder logic programming utility (RSLogix500). Entries in the 

file are static and read-only from the module’s perspective (e.g. 

time vs. position based operation). This file is automatically 

downloaded to the module when you switch the SLC processor to Run mode. 

The development software enables you to program the module from a 

personal computer connected to either the module’s DH485 or PRT1 

ports. The software allows direct access to the module through 

terminal emulation over an RS-232/423 or DH485 network.

Refer to the BASIC Development Software Programming Manual, 

publication 1746-PM001, for additional information on the software.

Typical Configurations

The typical configuration of the SLC system that incorporates your 

BASIC or BASIC-T module depends on whether the module is:

• integrated with a SLC 500 fixed or modular controller.

• programmed directly with an ASCII terminal or programmed 

using a personal computer with the BASIC development 

software, 1747-PBASE.

• communicating with a DH485 network or with an external 

source through a modem using DF1 protocol.

Module Integration

The module is a single-slot module that is inserted into a slot in the 

expansion chassis of your SLC 500 fixed controller or an open slot in 

the 1746 I/O chassis of your SLC 500 modular controller. The module 

may be inserted in any slot of the 1746 I/O chassis except the first slot 

of the first chassis, which is reserved for the SLC modular processor. 

Typical SLC fixed and modular configurations are shown in the 

following figures.

The BASIC development software provides the user with a structured 

and efficient means to create BASIC programs for the module. This 

software is loaded into a an MS-DOS compatible personal computer. It 

uses the personal computer to facilitate editing, compiling 

(translating), uploading, and downloading of BASIC programs. 

The BASIC development software has a menu-driven, window-type 

environment that offers: 

• pull-down menus to access all editor functions.

• function key access to frequently used functions.

• multiple window editing.

• cut and paste support between windows.

• search and replace support.

• search between files support.

• built-in calculator that can paste results into your program.

• ASCII look-up table.

• line draw editor to create operator interface images without having to enter ASCII characters.

• keystroke macros.

• undo and redo functions.

• extensive help messages for each menu, menu option, and for keywords embedded in the menu text.

• capability to create user-defined macro libraries.

• sophisticated debug tools including watch windows, single-step 

operation, and go to cursor breakpoint operation.

• syntax checked translations to native BASIC to reduce debug time.

• BASIC translator that steps through the BASIC program and identifies errors.

• ASCII terminal mode.

• hex file transfer support.

Software Features

The module provides the following software features.

• BASIC programming with the Intel BASIC-52 language and enhancements

• SLC 500 backplane data read and write support including image 

table transfers and M0 and M1 file transfers

• Execution of programs from memory modules

• String manipulation support

• DH485 network support

• DF1 protocol support

• Full set of trigonometric function instructions

• Floating point calculations and conversion

• Extensive call libraries

Module Communication Ports

There are three communication ports on the front of the module. The 

location, name, and pin numbers of these ports are listed on the 

inside of the module door. 

They are:

• PRT1 – Used to interface the module with user devices. This port 

is a serial port that accommodates RS-232/423, RS-422, and 

RS-485 communication modes. Port PRT1 is capable of operating 

full-duplex at 300, 600, 1200, 2400, 4800, 9600, and 19200 Kbps. 

The default settings are 1200 Kbps, RS-232/423 communications.

• PRT2 – Used to interface the module with user devices or a 

modem using DF1 protocol. This port is a serial port that 

accommodates RS-232/423, RS-422, and RS-485 communication 

modes. Port PRT2 is capable of operating full-duplex at 300, 600, 

1200, 2400, 4800, 9600, and 19200 Kbps.

• DH485 – Used to interface the module with the DH485 network. 

This port is not isolated and cannot directly drive the DH485 network. 

You must use a 1747-AIC link coupler to link port DH485 with the DH485 network.

BASIC and BASIC-T Modules

The modules are single-slot modules that reside in a SLC 500 fixed or modular controller chassis.

Use the module as:

• a foreign device interface.

• an operator interface.

Hardware Features

The module provides the following hardware features.

• 24 KB of battery backed RAM for storage of user programs and data

• Capacitive backup of RAM during battery change

• Socket for a standard 1747-M1, M2, M3, or M4 memory module 

(1746-BAS module) for nonvolatile storage of user programs

• Socket for a 1771-DBMEM1 or -DBMEM2 memory module 

(1746-BAS-T module) for nonvolatile storage of user programs

• Battery-backed, 24-hour clock/calendar

• Free-running clock with 5 ms resolution

• Two isolated 9-pin D-shell serial ports (PRT1 and PRT2) that 

provide RS-232/423, RS-422, and RS-485 communication with I/O devices

• One PRT2 port provides DF1 full-duplex or half-duplex slave 

protocol for SCADA applications

• One RJ-45 port (DH485) that provides communication over the DH485 network

• Multiple LED indicators for operator interface

• SLC 500 backplane interface