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ADVANCED FUNCTIONS
I/O DATA OUTPUT AREA
MAPPING
8–10
The following figure shows mailbox commands to set 1 to 4 attributes.
Attribute 1 length = 2 bytes
Attribute 2 length = 4 bytes
Attribute 3 length = 2 bytes
Attribute 4 length = 2 bytes
Figure 8-9: Mailbox example for IO data input mapping
This command makes it possible to map attributes in the I/O data output mapping object
(class A1h). By mapping data, a Get_Attribute_Single command or a Set_Attribute_Single
command from the DeviceNet master to the I/O data output mapping object can return a
specified block of data or write a block of data. Up to 6 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 output 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 output mapping object class A1h are directly mapped to
assembly object 04h instances as given below.
Class A1h, instance
Corresponding instance in assembly
01h, attribute
object class 04h (attribute 03h)
1
96h
2
97h
3
98h
4
99h
5
9Ah
6
9Bh
D485 MODBUS TO DEVICENET CONVERTER – USER GUIDE
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