A-B Addressing for PLC-5 I/O racks
This is how I keep it straight.
If you want your card arrangement totally unrestricted, it follows this pattern:
2-slot addressing = 8 point cards
1-slot addressing = 16 point cards
1/2-slot addressing = 32 point cards
I think of this as the 'default' configuration.
If you can tolerate alternating input cards and output cards in pairs, it follows this pattern:
2-slot addressing = 16 point cards
1-slot addressing = 32 point cards
1/2-slot addressing = not useful
I think of this as the 'upgrade' configuration. Many older PLC-2 and PLC-5 PLCs were originally installed with 8 point cards and 2-slot addressing. Over the years they were upgraded by replacing 8-point cards with 16-point cards. For example, if you had 2 8-point output cards in the same module group, you could replace them both with one 16-point output card and gain a spot for a new 16-point input card.
I don't think I would ever build a new system with alternating input and output cards. The ratio is usually more like 4 inputs for every output in my experience so I don't find that arrangement very useful. But when you need to squeeze a few more I/O into an existing system, definitely.
This is how I keep it straight.
If you want your card arrangement totally unrestricted, it follows this pattern:
2-slot addressing = 8 point cards
1-slot addressing = 16 point cards
1/2-slot addressing = 32 point cards
I think of this as the 'default' configuration.
If you can tolerate alternating input cards and output cards in pairs, it follows this pattern:
2-slot addressing = 16 point cards
1-slot addressing = 32 point cards
1/2-slot addressing = not useful
I think of this as the 'upgrade' configuration. Many older PLC-2 and PLC-5 PLCs were originally installed with 8 point cards and 2-slot addressing. Over the years they were upgraded by replacing 8-point cards with 16-point cards. For example, if you had 2 8-point output cards in the same module group, you could replace them both with one 16-point output card and gain a spot for a new 16-point input card.
I don't think I would ever build a new system with alternating input and output cards. The ratio is usually more like 4 inputs for every output in my experience so I don't find that arrangement very useful. But when you need to squeeze a few more I/O into an existing system, definitely.
- '1-slot' addressing means that each physical slot is allocated one logical 'Group', which has 16 bits of Input data and 16 bits of Output data. Putting a 32-bit Input module into Rack 01, Group 0 means that it will use up Word 0 and Word 1 of the Input data table.
- Addressing the seventh bit (bit number 6) on a discrete output card plugged into slot 3 would require the label O:3/6. In either case, the numerical structure of that label tells you exactly where the real-world input signal connects to the PLC.
February 11th, 2016, 05:03 AM
Hi,
I need to add two I/O cards to a PLC5 installation.
(one 16 bit input and one 16 bit output card)
The processor is a 5/40L
In RSLogix 'Processor Status' it shows bits 11 and 12 in word S:2 set for '2 Slot addressing'
Does this setting fix the method for all Racks? Hence no need for me to remove racks to check the dip switches?
Current set up (Also see attached pics)
There are 4 racks...
Rack 0 (4 Slot?) with...
PLC5 Processor and Analogue input card + 2 spare slots
Rack 1 (12 Slot) with...
Servo Controller and Servo Expander modules, plus RS232 I/F + 7 spare slots
Rack 2 (16 Slot) with...
Various 16 bit Digital I/O but O:027 not used
(if I remember rightly 027 address used internally? PLC2 hangover?)
Rack 3 (16 Slot) with...
Various 16 bit Digital I/O
Rack 4 (16 Slot) with...
Various 16 bit Digital I/O with some spare slots for output cards ONLY (2 Slot Addressing)
I was hoping to add one 16 bit input and one 16 bit output card to rack 1 but not sure about mixing the 16 bit cards with the Servo cards which are block transferred (8 bit?) I read something about this 'mixing' problem somewhere. (Suspicious about the remainder of this rack not being used by manufacturer!)
Although, installation was originally PLC2 (see old processor still in panel) not sure if this is relevant?
To summarise, my questions are...
Based on processor status file word S:2 will all racks dip switches be set for 2 slot addressing?
Can I install one 16 bit input and one 16 bit output card into rack 1?
Thanks in advance
See attachments of the installation
I need to add two I/O cards to a PLC5 installation.
(one 16 bit input and one 16 bit output card)
The processor is a 5/40L
In RSLogix 'Processor Status' it shows bits 11 and 12 in word S:2 set for '2 Slot addressing'
Does this setting fix the method for all Racks? Hence no need for me to remove racks to check the dip switches?
Current set up (Also see attached pics)
There are 4 racks...
Rack 0 (4 Slot?) with...
PLC5 Processor and Analogue input card + 2 spare slots
Rack 1 (12 Slot) with...
Servo Controller and Servo Expander modules, plus RS232 I/F + 7 spare slots
Rack 2 (16 Slot) with...
Various 16 bit Digital I/O but O:027 not used
(if I remember rightly 027 address used internally? PLC2 hangover?)
Rack 3 (16 Slot) with...
Various 16 bit Digital I/O
Rack 4 (16 Slot) with...
Various 16 bit Digital I/O with some spare slots for output cards ONLY (2 Slot Addressing)
I was hoping to add one 16 bit input and one 16 bit output card to rack 1 but not sure about mixing the 16 bit cards with the Servo cards which are block transferred (8 bit?) I read something about this 'mixing' problem somewhere. (Suspicious about the remainder of this rack not being used by manufacturer!)
Although, installation was originally PLC2 (see old processor still in panel) not sure if this is relevant?
To summarise, my questions are...
Based on processor status file word S:2 will all racks dip switches be set for 2 slot addressing?
Can I install one 16 bit input and one 16 bit output card into rack 1?
Thanks in advance
See attachments of the installation
Plc 5 1 Slot Addressing System
Feb 12, 2016 It is possible to assign 1/4, 1/2, 3/4 and 1 rack at a time. For example if 1-slot addressing is used, and only a 1/2 rack is assigned to chassis 1, then only the first 4 slots are available in that chassis. Probably not the case, but you should investigate it. In RSLogix 5 look in the IO Configuration - chassis table.