svn://software/hardware/LC4D/100218/docs/LC4D_MAN.doc
MRR
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PLC Expansion
PLC I/O expansion is possible through the four “PLC ADD” connectors. Each PLC expansion port can
accept 16 – 128 inputs, outputs, or inputs and outputs in 16 bit increments. This allows for digital I/O, DACs,
ADCs, or other devices to be added to the system as needed.
PLC ADD 1 – 4 Connector Pinouts
DATA TO EXPANSION CARD -
DATA TO PLC -
-12V
1
2
3
4
5
6
7
8
9
10
11
12
PLC ADD
+12V AND -12V RETURN *
+5V
CLOCK -
DATA TO PLC +
5V RETURN *
CLOCK +
* +12V AND -12V RETURN and 5V RETURN are connected on the Oak
5V RETURN *
DATA TO EXPANSION CARD +
+12V
PLC Expansion Memory Assignments
PLC I/O is arranged in 16 bit groups or slots. As a general rule, slots 0-14 are used for individual I/Os
such as switches and have a programmable debounce time for the inputs. Slots 15-47 are reserved for ADCs,
DACs, or other devices that do not require debounce. Every device using I/O space must use space in 16 bit
multiples by reserving slots. PLC expansion boards with inputs and outputs must have a matching number of
input and output slots.
Assignment of I/O slots occurs in a linear fashion starting at the Oak, then “PLC ADD” port 1, “PLC
ADD” port 2, etc. In the following general example, the Oak I/O is shown in its fixed location, which can not
be changed. Other devices may change locations if they are plugged into PLC ADD ports in a different order.
PLC ADD port devices that require debounce will be assigned starting at the slot marked “A”, while devices
that do not require debounce will start being assigned at the slot marked “B”.
Oak uses 6 slots for its inputs and 2 slots for outputs. Since I/O space must be reserved in 16 bit
increments, some I/O space is lost. For example, the Oak has 12 bit analog inputs which reserve 16 bits each,
leaving 4 input bits unused per analog channel. Also note that Oak inputs and outputs are not assigned
contiguously. The individual outputs take slot 0, while the DAC is assigned to the non–debounce / group output
area starting at slot 15. The individual (debounced) inputs take slot 0, while the ADCs are assigned to the non–
debounce / group input area starting at slot 15.
PLC Program INP / OUT, Slot, and I/O Area Relationship
Summary of Contents for OAK
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