PLC5 lose program on after power down

We have a PLC5/20 with a local rack of 120VAC I/O's and a RIO connection to a PV. Once in a while, if we power down the PLC to do maintenance work, the program would get erased when we power it back up. There's a line filter in front of the PLC power supply. This happens randomly and once we re-download the program, everything is ok again. Before I change out the power supply and the rack, is there something else I may be missing? Could the IO module be the cause as well? And yes, the battery is ok.

I was just at a site where the rack DIP switches were not being read correctly by the processor. Two of those switches define how the processor reads from an EEPROM may that may be present in the processor. In my case I had an EEPROM module stuck into the processor and the processor read off of this every time we powered up. This happened even though the switch settings should have caused the processor to only read off the EEPROM if the processor RAM was invalid. I toggles all the DIP sitches on the backplane and set them back to their original positions and everything was cool.

If you don't have an EEPROM module in the PLC and the processor THINKS it is supposed to read off of an EEPROM on power-up, you may get this reaction.

Keith

Hey, thanks Keith. I'll check that out.

Well, I haven't replace the PS or rack and the problem still does happen a few times since. I was able to get a crash log and hope someone can help me out with.

Fri Apr 13 08:43:31 2007 from RSLogix5 v6.10.10.35
Diagnostic Data for Processor PLC5/40 Series D Revision B
Domino Plug 1 Firmware Series/Rev: A/P
Domino Plug 2 Firmware Series/Rev: A/P
Fault logged by microprocessor: UPA
Error string: ".....up1: hardware fault=00088 at address 37ad0"
D0 = 0x0000001A A0 = 0x0020429E
D1 = 0x00000007 A1 = 0x0029C24E
D2 = 0x0000FFFF A2 = 0x0020D07A
D3 = 0x00000000 A3 = 0x0003B90A
D4 = 0x18200000 A4 = 0x0019BF60
D5 = 0x00000000 A5 = 0x0020842A
D6 = 0x00000016 A6 = 0x002042C4
D7 = 0x00000001 A7 = 0x00204290
Error Code = 0x0088
Trap Offset = 0x0000
Return address = 0x00037AD0
68Ks Status Register = 0x2000
Following are 26 words of stack data in hex
0000 0040 0001 B512 0007 0007 0000 0008 0020 42C2 0000 0040 0000 0000 1820
0000 FFFF 000E 0008 5DC9 0019 7694 0000 0020 4326 0003
Raw Data of above
0x1988FA 00 01 00 00 00 1A 00 00 00 07 00 00 FF FF 00 00 ................
0x19890A 00 00 18 20 00 00 00 00 00 00 00 00 00 16 00 00 ... ............
0x19891A 00 01 00 20 42 9E 00 29 C2 4E 00 20 D0 7A 00 03 ... B..).N. .z..
0x19892A B9 0A 00 19 BF 60 00 20 84 2A 00 20 42 C4 00 20 .....`. .*. B..
0x19893A 42 90 00 88 00 00 00 03 7A D0 20 00 00 00 00 40 B.......z. ....@
0x19894A 00 01 B5 12 00 07 00 07 00 00 00 08 00 20 42 C2 ............. B.
0x19895A 00 00 00 40 00 00 00 00 18 20 00 00 FF FF 00 0E ...@..... ......
0x19896A 00 08 5D C9 00 19 76 94 00 00 00 20 43 26 00 03 ..]...v.... C&..
0x19897A 07 07 07 0D 0A 75 70 31 3A 20 68 61 72 64 77 61 .....up1: hardwa
0x19898A 72 65 20 66 61 75 6C 74 3D 30 30 30 38 38 20 61 re fault=00088 a
0x19899A 74 20 61 64 64 72 65 73 73 20 33 37 61 64 30 0D t address 37ad0.
0x1989AA 0A A6 00 AB 00 49 00 01 00 88 00 B0 00 43 00 0D .....I.......C..
0x1989BA 00 45 00 61 00 D1 00 C5 00 41 00 C0 00 26 00 46 .E.a.....A...&.F
0x1989CA 00 90 00 20 00 CC 00 45 00 E9 00 00 00 01 00 98 ... ...E........
0x1989DA 00 52 00 01 00 00 00 14 00 90 00 90 00 40 00 28 .R...........@.(
0x1989EA 00 40 00 22 00 93 00 2B 00 00 00 48 00 43 00 00 <A href="mailto:.@."...+...H.C">.@."...+...H.C..
0x1989FA 00 60 00 2C 00 84

Based on Error Codes, check the RIO connectors on both ends, and the cable to the Panelview:

MSG Instruction Error Codes
Errors detected by the processor:
Code:
Enhanced PLC-5 Classic PLC-5 Ethernet only Description:
0002 2 Link layer timed out or received a NAK
0003 3 Duplicate token holder detected by link layer
0004 4 Local port is disconnected
0005 5 Application layer timed out waiting for a response
0006 6 Duplicate node detected
0007 7 Station is off line
0008 8 Hardware fault
0037 55 0037 Message timed out in local processor
0089 137 0089 Processor’s message buffer is full
0092 146 0092 No response (regardless of station type)
© 1997 Rockwell Software Inc.

Click to expand...

Thanks for the help guys. I've checked the cable and the PV and CPU was recently replaced. I guess I need to find the downtime and swap out the PS/Rack.