Knowledge Base /
Technical Notes
Integration of AB SLC RIO Racks to the PLC IO Interface
By Geoff Nash
Product: PLC IO Interface

This technical note shows the hardware configuration required to make Allen-Bradley SLC IO Racks work with the PLC IO Interface.

Introduction

Allen Bradley SLC remote I/O racks may be interface to DeltaV using the AB 1747-ASB module to connect with the PLC IO module. This module may replace the SLC controller for local I/O racks. The SLC 1747-ASB appears on the 1771 RIO network as one or more racks depending on the I/O table size specified in the ASB. There are two steps to integrate the 1747-ASB module into the PLC IO module, first make sure the network is correctly terminated, the check and modify the 1747-ASB DIP switches for the connection.

To terminate the communication channel with the PIO first modify the resistor in the PIO to match the required terminating resistor for the SLC RIO racks. The SLC rack uses an 82-Ohm resister as a terminator. If no resistor is present messages may be lost and the rack communications may be interrupted (faulted). As an 82-Ohm is used, the one in the PI’s default 15O-Ohm must be modified for this link, from page 16 of the MYNAH AB 1771 PIO (IOD-5102) manual:

Next configure the ASB to communicate with the PIO. The information and the DIP switch settings on 1747-ASB are taken from the Allen-Bradley Remote I/O Adapter Module manual (Publication 1747-UM006B-EN-P June 2003). This document presents the configuration of this module specifically for communications to the PIO module, for a more detailed discussion of the general configuration process and 1747-ASB parameters consult the Allen-Bradley manual. Most switch settings are configured to match the system requirements of the user. Several switch settings must be specific for communications with the PIO, and for others PLC Explorer must be configured to match the settings.

The module is configured using three DIP switches; each of these is detailed below.

Switch 1 Logical rack and starting group settings


1-6 ON-ON-ON-ON-ON-ON Rack number, example here is rack 0. These 6 switches specify a 6-bit number with bit 0 (LSB) specified by switch 6 (valid values of from 0-32). An OFF switch means the bit is set (i.e., ON-ON-ON-OFF-OFF-ON = 000110 or 6. The combinations are show below must match the selected rack number specified in PLC Explorer.

1
2
3
4
5
6
Logical Groups
Decimal
Octal
ON
ON
ON
ON
ON
ON
0
0
ON
ON
ON
ON
ON
OFF
1
1
ON
ON
ON
ON
OFF
ON
2
2
ON
ON
ON
ON
OFF
OFF
3
3
ON
ON
ON
OFF
ON
ON
4
4
ON
ON
ON
OFF
ON
OFF
5
5
ON
ON
ON
OFF
OFF
ON
6
6
ON
ON
ON
OFF
OFF
OFF
7
7
ON
ON
OFF
ON
ON
ON
8
10
ON
ON
OFF
ON
ON
OFF
9
11
ON
ON
OFF
ON
OFF
ON
10
12
ON
ON
OFF
ON
OFF
OFF
11
13
ON
ON
OFF
OFF
ON
ON
12
14
ON
ON
OFF
OFF
ON
OFF
13
15
ON
ON
OFF
OFF
OFF
ON
14
16
ON
ON
OFF
OFF
OFF
OFF
15
17
ON
OFF
ON
ON
ON
ON
16
20
ON
OFF
ON
ON
ON
OFF
17
21
ON
OFF
ON
ON
OFF
ON
18
22
ON
OFF
ON
ON
OFF
OFF
19
23
ON
OFF
ON
OFF
ON
ON
20
24
ON
OFF
ON
OFF
ON
OFF
21
25
ON
OFF
ON
OFF
OFF
ON
22
26
ON
OFF
ON
OFF
OFF
OFF
23
27
ON
OFF
OFF
ON
ON
ON
24
30
ON
OFF
OFF
ON
ON
OFF
25
31
ON
OFF
OFF
ON
OFF
ON
26
32
ON
OFF
OFF
ON
OFF
OFF
27
33
ON
OFF
OFF
OFF
ON
ON
28
34
ON
OFF
OFF
OFF
ON
OFF
29
35
ON
OFF
OFF
OFF
OFF
ON
30
36
ON
OFF
OFF
OFF
OFF
OFF
31
37

7-8 ON-ON Starting group example rack(s) start at group 0. These 2 switches specify a 2-bit number with bit 0 (LSB) specified by switch 8. Values specify quarter rack 0-3 (group 0 to 6, as a quarter chassis holds 2 groups). An OFF switch means the bit is set (i.e., ON-OFF = 01 or 1 (group 2). The combinations are show below must be 0 for full rack, or match the partial rack specified in PLC Explorer.

7
8
Starting Group
ON
ON
0
ON
OFF
2
OFF
ON
4
OFF
OFF
6

Switch 2 Settings

 

1-2 ON-ON Example of 57.6 Baud rate, must match that specified in PLC Explorer.

 

1
2
Starting Group
ON
ON
57.6K
ON
OFF
115.2K
OFF
ON
230.4K
OFF
OFF
Invalid

3 ON Primary chassis (normally for the PIO this will be primary, unless complementary IO is specified in PLC Explorer.

4 ON Reserved??? Note different diagrams for this switch show 3& 4 swapped, I 3 as this is the detail, but as the reserved switch setting is ON, as long as this is a primary chassis both may be set to ON and there is not a problem.

5-8 OFF-OFF-ON-ON SLC Chassis size, this is configured to fill the IO table(s) in the PLC. This example shows 1 full rack, these switches set a 4-bit value with bit 0 being switch 8. The value created is one less than the number of logical quarter racks configured. A quarter rack is 2 IO groups (8 bits of discrete data) or 16 bits. An OFF switch means the bit is set (i.e., ON-OFF-OFF-ON == 0110 or 6 (7 quarter racks or 14 groups). The combinations are show below.

5
6
7
8
Logical Groups
ON
ON
ON
ON
2
ON
ON
ON
OFF
4
ON
ON
OFF
ON
6
ON
ON
OFF
OFF
8
ON
OFF
ON
ON
10
ON
OFF
ON
OFF
12
ON
OFF
OFF
ON
14
ON
OFF
OFF
OFF
16
OFF
ON
ON
ON
18
OFF
ON
ON
OFF
20
OFF
ON
OFF
ON
22
OFF
ON
OFF
OFF
24
OFF
OFF
ON
ON
26
OFF
OFF
ON
OFF
28
OFF
OFF
OFF
OFF
30
OFF
OFF
OFF
OFF
32

The setting here configures logical racks in the PIO. The number of logical racks actually created depends on the addressing mode (1, 2, or ½ slot addressing), the starting group, and the number of groups specified here. Not there may be problems if not all physical slots in chassis are accounted for in the size selection and actual IO modules are placed in the slots physical slots excluded (see AB document for details).

Switch 3 Settings

1 ON/OFF Choice to hold last state (ON) or go to 0 (OFF). This is site specific and has no setting in PLC Explorer.

2 ON Restart processor automatically (if OFF power to the rack must be cycled for PIO to start communications).

3 ON Must be Restricted (ON) i.e., longer response time for 57.6 and 115.2). This is required for PIO, this is the equivalent to Series B emulation in 1771-ASB.

4 OFF Last chassis ON (not last chassis) or OFF (last chassis for rack) depending on other chassis configuration. This example specifies this is the last chassis present for the rack (if partial, no other chassis will supply the IO data).

A 1747-ASB module should be configured as the last chassis when:

  • It's image crosses logical rack boundaries and no other adapter uses a higher group number within it's last logical rack.
  • it uses a portion of a logical rack and no other adapter uses a higher group number within that logical rack.

5-6 ON-OFF Example uses 1-slot addressing; this must match the setting in PLC Explorer

6
6
Starting Group
ON
ON
Invalid
ON
OFF
1-slot addressing
OFF
ON
2-slot addressing
OFF
OFF
½ slot addressing

7 OFF Must be set to block transfer mode (OFF), this is required for the analog modules (discrete modules always use the discrete image table).

8 ON Must be ON (save mode) after making changes (or rack will not accept the changes), power-up the chassis, then power down and set switch 8 to OFF to prevent further changes.