ProSoft Technology ProLinx S3964R User Manual download pdf (Page 39)

Publication LOGIX-AP010B-EN-P - May 2010 39

Software Conversions - Program Structure Chapter 2

With the Add-On Instruction a pre-scan routine can be configured to run

when the controller goes from Program mode to Run mode, or powers up in

Run mode. Under these conditions, the pre-scan routine will run once, and can

typically be used to initialize data. This is not available with Step 5 Function

Blocks.

An Add-On Instruction can have an EnableInFalse routine, which will be

called (if present) when the rung condition at the Add-On Instruction call is

false. In this case, the input and output parameters will pass values.

Watchdog Timer

A watchdog timer can be configured for each RSLogix 5000 task. This timer

specifies the maximum time a task can run before triggering a fault.

In S5 the user configures the cycle time in 54 DX0 or OB26. An error is

triggered if a scan of the program is not executed within this time. There is no

facility to set watchdog timers for individual blocks in S5. The S5 watchdog

timer can be retriggered by calling OB 222.

I/O Addressing

In Step 5 and RSLogix 5000 software, the software address of a physical input

from the plant is determined by the position of the input card and the channel

to which the input is connected.

Similarly, the software address of a physical output to the plant is determined

by the position of the output card and the channel to which the output is

connected.

Example

In Step 5, if an input is connected into the 3rd channel on the first input card,

it is assigned the address I0.2. (The first channel on this card is assigned

address I0.0). Using the Step 5 symbols table, the programmer can assign a

name to each input/output as shown below.

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 139 140

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ProSoft Technology ProLinx S3964R User Manual Page 39