Rockwell Automation 1771-IS User Manual

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Introduction 1-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General 1-1 Typical

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Applications

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1-2

Module Preparation, Wiring and Installation 2-1 . . . . . . . . . . . . . .

General 2-1 Switch Wiring 2-4 Additional Keying 2-11

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Selection of Operating Modes

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Considerations

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2-1

2-10

Programming and Operation 3-1 . . . . . . . . . . . . . . . . . . . . . . . . . .

General 3-1 Module Scan of Switch Contacts Storage Block

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of Switch Contact Data

ransfer of Switch Data

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3-1 3-1

3-14

Specifications A-1

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Introduction

Chapter

General

The 1771-IS DC (5V) Multiplexer Input Module, Figure 1.1 reads the status of up to 72 hard contact switch devices through one I/O slot. This information is transferred to the PC processor by block transfer programming. The module can be used with any Allen-Bradley programmable controller that has block transfer capability, an expandable data table, and uses the 1771-I/O structure.

Figure 1.1 DC

(5V) Multiplexer Input Module

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When thumbwheel switches are used with the module, user-selectable operating modes can be selected for convenient storage of 3-digit and 4-digit BCD thumbwheel data. An additional mode is provided that latches the input of momentary contact devices such as pushbutton or keyboard switches.

The module performs self diagnostics during its initial power-up sequence. If a memory failure is detected at any time, the fault LED on the front panel will illuminate and the module will not operate.

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The module reads the status of switch contacts by enabling and reading a “bank” of 8 contacts at a time. This requires that the contacts be grouped and that diode decoupling be used to prevent the appearance of a “phantom” contact closure. Up to 9 banks of 8 contacts per bank can be handled by the module. Power to the switch banks is provided by the module.

Contact scanning occurs until the module is interrupted by a read instruction from the PC processor. Contact status is stored in on-board RAM memory until the module outputs the contact status to the processor. Therefore switch scanning by the module is totally independent of I/O scanning by the processor. Module scanning is user-selectable at a normal or fast rate with contact de-bouncing.

Typical Applications

In many applications, it is necessary to set or change the preset values of timers or counters or the values of process variables. It is convenient to do this using BCD thumbwheel switches (Figure 1.2). Applications that require the use of multiple thumbwheel switches include, but are not limited, to the following:

control of chemical processes production-part adjustments used in the automatic balancing of tires control of pallets in materials handling cycle time adjusments in production machines and processes

Figure 1.2 Typical

3-digit Thumbwheel Switch

–

The DC (5V) Multiplexer Input Module saves I/O space and user program. It can handle the switch input from up to six 3-digit or four 4-digit BCD thumbwheel switches. It can also handle up to 72 discrete contact switches.

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WARNING: Outputs of any output module may temporarily change operating state at power-up if placed in the same I/O chassis with a multiplexer module, cat. no. 1771-IS, earlier than hardware revision D, and a power supply (or processor with self-contained power supply) other than 1771-P1 or 1771-P2. To avoid damage to equipment and/or injury to personnel use only multiplexer modules, cat. no. 1771-IS, hardware revision D or later.

Important: Hardware revision D is designated by part no. XXXXXX-XX/D on the module nameplate. Earlier modules (cat. no 1771-ISC) do not have this part no./D designation.

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Chapter

Module Preparation, Wiring and Installation

General

Switch Selection of Operating Modes

The modes of operation must be set internally to suit the conditions under which the module will be used. In addition, switch contacts and decoupling diodes must be wired to the module.

The module is capable of operating in a variety of modes depending on the kinds of switches connected to it, whether the module is placed in a local or remote I/O rack, and/or whether latched data in module memory will be reset automatically or by program logic after the transfer of data.

The mode selection switch is mounted near the lower rear corner of the printed circuit board under the left side cover of the module. It is accessible by removing the four slotted cover screws on the right side of the module.

The modes are selected by setting the mode selection switches ON or OFF according to the positions defined in Figure 2.1.

2-1

Chapter 2

Module Preparation, Wiring, and Installation

Figure 2.1 Mode

Selection Dip Switch

OFF

ON Momentary (Latched) Contact Mode

OFF

Always OFF

16–Bit Data 12–Bit Data

Fast Normal

Maintained Contact Mode

Always OFF

Program Initiated Reset Automatic Reset

1234567

O N

O F F

Switch #1 - Always OFF.

Switch #2 - 16 Bit Storage/12 Bit Storage, Select 12-bit storage when using 3-digit BCD thumbwheel switches. Select 16-bit storage when using 4-digit BCD thumbwheel switches, discrete momentary contact switches, or discrete maintained contact switches. (ON for 16-bit storage, OFF for 12-bit storage.)

Switch #3 - Normal Scan/Fast Scan. The module scan is independent of the processor scan and is generally set at the normal (15.3 msec) position. The fast scan (5.1 msec) can be used when operating in either the

OFF

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Chapter 2

Module Preparation, Wiring and Installation

momentary (latched) contact mode or maintained contact mode. (ON for fast scan, OFF for normal scan.)

Switch #4 - Maintained Contact Mode/Momentary (latched) Contact Mode. Select the maintained contact mode when storing the status, ON or OFF, of maintained switch contacts. Their status is updated in every scan. Select the momentary (latched) contact mode when storing momentary OFF-ON switch contact transitions. Subsequent scans will not reset latched bits even if the corresponding switches are reopened. The transition is latched ON in module memory and must be reset after the latched data is transferred to the processor. [ON for momentary (latched) contacts, OFF for maintained contacts.] The position of SW #4 will also affect data byte storage. See the diagrams in chapter 3 for further detail.

Switch #5 - Always OFF.

Switch # 6 - Always OFF.

Switch # 7 - Program Reset/Automatic Reset. Select program reset when momentary (latched) switch status data is to be reset by setting a bit in a user program instruction. Refer to section titled “Other Programming Considerations, PLC-2 Family and PLC-3.” Select automatic reset when momentary (latched) switch data is to be reset automatically. This switch is not functional when the module is operating in the maintained contact mode. (ON for program reset, OFF for automatic reset).

Important: When using momentary contact mode in remote applications, only the program reset mode should be selected. Use program reset to guard against loss of data during transfer to the processor. When using momentary contact mode in local I/O applications, either the program reset or automatic reset can be selected.

The allowable combinations of module operating modes are summarized in Figure 2.2.

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Module Preparation, Wiring, and Installation

Figure 2.2 Allowable

Normal Scan Fast Scan

Operating Modes

1771-IS Multiplexer Module

12–Bit

Maintained Contacts

Momentary (latched) Contacts

16–Bit

Program Reset Automatic Reset

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Wiring

2-4

The wiring and programming of the module are dependent on each other. Switch assemblies should be wired according to the wiring schematics presented in this chapter. If wired differently, the transfer of data may not take place or may become scrambled.

Module Wiring

Connections to the module are made through a removable field wiring arm connector (cat. no. 1771-WF) which allows the module to be

Chapter 2

Module Preparation, Wiring and Installation

removed or installed in the I/O rack without disconnecting the wiring.) The swingarm can be removed from the I/O rack at the pivot bar.

Thumbwheel Switch Wiring

Thumbwheel switch terminations are illustrated in Figure 2.3. Digit place labels refer to the position of each digit in a 3-digit or 4-digit thumbwheel switch as follows:

MSD and LSD - Most and Least Significant Digit; MD Middle Digit; UMD and LMD - Upper and Lower Middle Digit, respectively.

Thumbwheel switches are wired in parallel as shown in Figure 2.4 for 4-digit switches, and in Figure 2.5 for 3-digit switches. The four switch terminals numbered 8, 4, 2, 1 for each thumbwheel digit are wired respectively to field wiring arm terminals 2, 3, 4, 5 or 6, 7, 8, 9. Field wiring arm terminal 1 is not used.

4–Digit Thumbwheel

3–Digit Thumbwheel

Figure 2.3 Thumbwheel Terminations

Enable Lines

MSD

UMD

LMD

LSD

Enable Lines

Digit Place Labels

Switch Terminal Numbers

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Module Preparation, Wiring, and Installation

Figure 2.4 T

ypical Point-to-point W

Switch Contact Mode)

iring for Up to Four 4-digit Thumbwheel Switches (Maintained

Enable

SW4 SW3

8421 8421

SW2

MSD UMD LMD LSD MSD MSD

UMD UMD

LMD LMD

LMD

AABB

SW1

421 8421 8421 8421

LSDLMDUMDMSD

LSD LSD

4–Digit

Thumbwheel

Switch

(User Supplied)

Lines

G & H E & F C & D

2-6

8421

Field Wiring Arm 1771–WF

Digit Junction

Terminal Strip

(User Supplied)

8421

2346578

Module Inputs 7 6 5 4 3 2 1 0 ABCDEFGHI

10111213141516

Enable Lines

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Figure 2.5 T

ypical Point-to-point W

Contact Mode)

Chapter 2

Module Preparation, Wiring and Installation

iring for Up to Six 3-digit Thumbwheel Switches (Maintained Switch

Enable

Lines

SW6

MSD MD LSD MSD MSD MD LSD MSD

G, H, I D, E, F

MD LSD MD LSD

SW3 SW2SW5

8421 8421

3–Digit Thumbwheel Switch (User Supplied)

SW4

ABC MSD MD

LSD

MSD MD LSD

SW1

8421 8421 8421 8421 8421 8421

8421

Field Wiring Arm 1771–WF

Digit Junction Terminal Strip (User Supplied)

8421

2345678

1112131415

Module Inputs 7 6 5 4 3 2 1 0 I H G F E D C B A

Enable Lines

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Module Preparation, Wiring, and Installation

Important: The selection of the four field wiring arm terminals, either 2, 3, 4, 5 or 6, 7, 8, 9 is critical for correct transfer of switch status data.

The point-to-point wiring schematics show all electrical connections for the first of several parallel switch assemblies. The wiring of additional assemblies is shown conceptually (in the upper portion of each schematic). Switch lines 8, 4, 2, 1 are wired to each additional switch assembly using decoupling diodes identically to the first switch assembly. Enable line(s) for each additional switch assembly are specified in the conceptual part of the drawing.

The enable lines, A through I, are wired to field wiring arm terminals 18 through 10, respectively. Note that enable line A is connected to field wiring arm terminal 18, etc. It may be desirable to terminate thumbwheel switch lines 8, 4, 2, 1 at a terminal block on the switch panel. A single set of switch lines 8, 4, 2, 1 and enable lines should be contained in a shielded cable connecting the switch panel to the field wiring arm to minimize connections at the field wiring arm terminals.

Observe the following practices when wiring thumbwheel switches:

Bundle thumbwheel switch wiring separately from other wiring. Shielded cable is recommended. Ground the shielded cable only at the I/O rack. The shield must remain

ungrounded at the other end.

Discrete Switch Bank Wiring

Up to 72 discrete contact switches can be wired to the module as shown in Figure 2.6. These switches can be momentary contact or maintained contact switches. Refer to section titled “Thumbwheel Switch Wiring” for wiring guidelines and practices.

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