Watlow Electric Gateway & DeviceNet User Manual

Page 18

RUI/Gateway & DeviceNet

Configuration & Ladder Logic Example

Using an Allen-Bradley CompactLogix PLC

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transfer of data to and from the PLC and EZ-ZONE

controllers via simple copy instructions

in the PLC. The copy instruction also works nicely when all of the data types are not the same

such as when working with 8 bit, 16 bit, and 32 bit members. The copy instruction copies the

source to the destination byte for byte so there is no further conversion needed.

34. Because there are 4 entries for PM1 in the custom T to O and O to T assemblies above, that

must mean that the CIP Assembly Size for gateway instance 1 is equal to four. Using the

same logic, PM2 has 10 entries so the Assembly Size must be equal to 10, etc…

Gateway

Instance

CIP

Assembly

Size

Gtw = 1

A;nb = 4

Gtw = 2

A;nb = 10

Gtw = 3

A;nb = 2

Gtw = 4

A;nb = 4

As can be seen above, unless changed, the members that occupy any one of the 20 member

locations (or wherever the gateway instance changes) will be according to the factory

defaults. So, the first member of the T to O for any given gateway instance will always be

PV1 regardless of where it is placed in the assembly.

35. The first member of the T to O assembly above is identified as “Device Status “. This member

will always be present and explains why in step 15 that the input assembly size is shown as
84 bytes (21-32 bit words) different from the output assembly being 80 bytes (20-32 bit
words).

To better understand the above status word a couple of important facts related to Standard

Bus addressing must be explained. Lets first look at valid addresses (physical & logical) for

computers, RUIs, Communication cards (Masters, 0-15), and lastly, EZ-ZONE

controllers

(Slaves, 16-31). The logical addresses are set by the user. Look at the table below.