OK, lets pretend that slots 0-3 have 16pt discrete input cards and slots 4-7 have 16 pt. The chassis "knows" what addressing is used.Ī rack is a logical rack that consists of 8 groups. Now here is a very important point: The processor does not know what kind of chassis its in or what cards are in the chassis and it also does not know whether 1/2 slot, 1 slot, or 2 slot addressing is being used. Rather a group is used.Ī group can refer to 1/2 of a slot, a full slot, or two slots. Unlike the SLC, IO addressing in the PLC 5 is not fully dependent upon the slot the module is in. Slots 0-7 are occupied by discrete IO cards. Please note that it is called a chassis, not a rack. Here a PLC 5 is shown in a 12 slot chassis. If you were to use 32 point input cards then you must configure the rack to that two groups occupy one slot.īecause only 16 bits of input data and only 16 bits of output data are available for each group then specialty IO cards make use of block transfers to move that data to N files in the PLC. When using 1 group = 2 slot addressing the IO image table words can be conserved but then you must alternate input-output cards, that is, an input card and output card must be placed next to each other - both belong to the same group. Likewise, each output card wastes a word in the input image table. When using 1 group = 1 slot addressing, each input card wastes a word in the output image table. Depending on how the rack is configured, a group can occuy one physical slot, two physical slots, or 1 physical slot can be occupied by two groups (1/2 slot). A group is a logical slot location in the physical rack. In the PLC5 the I/O image table is fixed at 1 word of input and 1 word of output image per group. I would think that I should see 16 addresses listed in the input image table, as opposed to the 4 I listed above. The light on the input card is solid green, the fault LED is off. Getting back to the PLC/5 though, the remote I/O LED is on solid red and the PROC LED is on solid green. When I go into the input image table on the left-hand side, I change the radix from binary to decimal and then the addresses listed are as follows: The CPU is communicating with the PC and I am able to go online with the processor but I don't think it is seeing the input card properly. When I power up the rack, the remote light is on solid red. The problem I am having is that I am not sure whether I have my PLC 5 CPU running properly. I just want to see if the input card works, so I figured I could get in the input image table in RS Logix 5 and watch the decimal number change with the input I am testing. I have a PLC 5/15 processor and I am trying to run an analog input card (1771-IFE A) for testing purposes.
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