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ADVANCED FUNCTIONS
I/O DATA INPUT AREA
MAPPING
8–8
The following figure shows mailbox commands to set 1 to 4 attributes.
Attribute 1 length = 6 bytes
Attribute 2 length = 0 bytes
Attribute 3 length = 4 bytes
Attribute 4 length = 2 bytes
Figure 8-7: Mailbox example for parameter data output mapping
This command makes it possible to map attributes in the I/O data input mapping object
(class A0h). By mapping data, a Get_Attribute_Single command from the DeviceNet master
to the I/O data input mapping object can return a specified block of data. Up to six
attributes can be mapped in this object. Attributes are mapped with start of attribute 1.
The offset is set from the start of the I/O data input area and length specifies the amount of
bytes to map. Attribute 1 in the mailbox is followed by attribute 2, and continues to
attribute 6. If length is set to zero, the attribute will not exist. As such, it is possible to map
only object 1 and 5 by letting the length of attributes 2 through 4 be zero. It is only
necessary to include mailbox information up to the last attribute number.
If any offset or length is invalid, the length and offset will be set to zero in the mailbox
answer and the attribute will not be mapped.
The attributes of I/O data input mapping object class A0h are directly mapped to assembly
object 04h instances as given below.
Class A0h, instance
Corresponding instance in assembly
01h, attribute
object class 04h (attribute 03h)
1
64h
2
65h
3
66h
4
67h
5
67h
6
68h
D485 MODBUS TO DEVICENET CONVERTER – USER GUIDE
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