1756-OA16 I.FuseBlown Word

aj2004

Member
Join Date
Sep 2015
Location
burnaby
Posts
4
Hi there,

I'm using an AC output module (OA16) and I noticed the FuseBlown input word in my controller tags (Local:13:I.FuseBlown) and I don't quite understand what the bits represent.

I am familiar with the I.FuseBlown status word for a 1756-OB16E output module, for example. Each of the first 16 bits represents an electronic fuse for the corresponding output has "blown".

The user manual for digital I/O says that, for the OA16, each of the 2 groups of outputs (0-7 & 8-15) is fused internally. However, I can't figure out how the actual FuseBlown bits work for this module.

Does I.FuseBlown.0 = Group 0 (outputs 0-7), or Output 0?
If the Group 0 fuse blows, are the FuseBlown bits 0-7 set to 1s?
Or is FuseBlown.0 for Group 0, and FuseBlown.1 for Group 1?

Thanks!
 
aj2004 said:
Does I.FuseBlown.0 = Group 0 (outputs 0-7), or Output 0? - No
If the Group 0 fuse blows, are the FuseBlown bits 0-7 set to 1s? - Yes
Or is FuseBlown.0 for Group 0, and FuseBlown.1 for Group 1? - No

For the 1756-OA16 Output Module there are two internal fuses on the PCB for the two Groups of Output points -

Fuse in middle of PCB = Group 0 - Outputs 0-7
Fuse at bottom of PCB = Group 1 - Outputs 8-15

I.FuseBlown.0-.31 Indication...

Note: FuseBlown Input Word is a 32-bit DINT

When a fuse is blown the corresponding Group bits in the FuseBlown Input Word will be set to 1 as follows -

Group 0 = bits 0 through 7
Group 1 = bits 8 through 15
Bits 16 through 31 do nothing

Binary Representation...

Group 0 Fuse Blown = [31-0] 2#0000_0000_0000_0000_0000_0000_1111_1111
Group 1 Fuse Blown = [31-0] 2#0000_0000_0000_0000_1111_1111_0000_0000

The Blown Fuse LED indicator will illuminate if either Group fuse blows, but there must be a load on at least one Group Output for it to be detected, else the LED will not illuminate.

Regards,
George
 
Last edited:
Thanks for your help!

For anyone else that finds this thread, here is the logic I used to monitor these bits:


Lower Bits 0-7:

BTD (Bit Field Distribute)
Source: Local:13:I.FuseBlown
Source Bit: 0
Dest: Local_Slot13_FuseSts_Lower (DINT)
Dest Bit: 0
Length: 8

In series with a NEQ 0 to turn on a "FuseBlown_Lower" OTE


Upper Bits 8-15:

BTD (Bit Field Distribute)
Source: Local:13:I.FuseBlown
Source Bit: 8
Dest: Local_Slot13_FuseSts_Upper (DINT)
Dest Bit: 0
Length: 8

In series with a NEQ 0 to turn on a "FuseBlown_Upper" OTE


This could probably be done with AND instructions using a bitmask, but the existing logic in this routine uses BTDs, so I stuck with the same format.
 

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