Fieldbus - List of I/O commands

Modified on Thu, 13 May 2021 at 05:53 PM


Expandable fieldbus cards are used to expand the existing I/O available on the RC8/A controller. This also allows the controller to communicate to different industrial protocols to make it easier to handle communication to other devices. For DENSO, the command structure is very similar for most of our fieldbus options.

Here is a list of compatible fieldbus cards for the RC8/A controller as well as respective combinations of cards.

The parallel card is expandable discrete I/O for the RC8/A controller. This card can be combined with all the fieldbus options, as its allocation does not overlap with the fieldbus options.

Aside from CC-Link RD, all the fieldbus cards use similar allocation modes. There are two main allocation modes called Standard and Compatible. Standard mode is typically recommended as it maximizes the available I/O by multiplexing bits to execute different functions. Compatible mode is a throwback mode for older controllers that used dedicated bits for dedicated command. For example in compatible mode, if you have 8 bits, you can only do 8 different commands with those bits. Through Standard mode, these bits are multiplexed allowing you to perform many more commands with the same number of bits.

Inputs (Standard mode):

Here is a chart of inputs for Standard mode. You can also reference the link for the same chart. I am referencing the DeviceNET slave allocation as the different fieldbus options share the same allocation.

I/O port No.Signal name
512Step Stop (All tasks)
514Halt (All tasks)
515Strobe Signal
516Interruption Skip
519Command data area odd parity
520Data area 1, bit 0
521Data area 1, bit 1
522Data area 1, bit 2
523Data area 1, bit 3
524Data area 1, bit 4
525Data area 1, bit 5
526Data area 1, bit 6
527Data area 1, bit 7
528Data area 2, bit 0
529Data area 2, bit 1
530Data area 2, bit 2
531Data area 2, bit 3
532Data area 2, bit 4
533Data area 2, bit 5
534Data area 2, bit 6
535Data area 2, bit 7
536Data area 2, bit 8
537Data area 2, bit 9
538Data area 2, bit 10
539Data area 2, bit 11
540Data area 2, bit 12
541Data area 2, bit 13
542Data area 2, bit 14
543Data area 2, bit 15
544Command area, bit 0
545Command area, bit 1
546Command area, bit 2
547Command area, bit 3
552 … 767User input

List I/O Command

Our fieldbus options use a 4-bit command area, 8-bit data area 1, and a 16-bit data area 2. The combination of these bits execute specific commands. The following table shows what commands are available.

Command areaData area 1Data area 2Status area
Program Operation
00000001 Program reset startProgram number
00000010 Program startProgram number
00000100 Continue start*
00010000 Step stopProgram number
00100000 Instantaneous stopProgram number
01000000 ResetProgram number
10000000 Activation of Supervisory TasksProgram No.( 0xffff activates all supervisory tasks of root, 0xfffe activates all supervisory tasks)
10000001 Deactivation of Supervisory TasksProgram No. (0xffff deactivates all supervisory tasks)
External Speed and Acceleration Setting
00000001 Speed settingSet speed value
00000010 Acceleration settingSet acceleration value
00000100 Deceleration settingSet deceleration value
Error Read
Error number
Type I Variable Write
Type I variable numberSet variable value (lower 16 bits)
Type I Variable Read
Type I variable numberVariable value (lower 16 bits)
Mode Switching
00000001 Motor ON, CAL execution
00000010 External speed 100
10000000 External mode switching 10000011 Execution of all above (Motor ON -> CAL -> SP100 -> External)
Clear Robot Error
I/O Write
Set I/O valueFirst internal I/O port address
I/O Read
First internal I/O port addressI/O

The following timing diagram can be referenced for executing commands from your PLC. 

For executing a program from an external device, such as a PLC, you must make sure the STEP STOP (ALL TASKS) and HALT (ALL TASKS) inputs are normally ON. Failing to do so will prevent the program from executing.

Owner's Manual

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