I/O Data Vs. Explicit Data - GE D485 Instruction Manual

I/O DATA VS. EXPLICIT
DATA
D485 MODBUS TO DEVICENET CONVERTER – USER GUIDE
Data exchange on the fieldbus interface is based on the standard DeviceNet objects, and
five vendor specific objects. The vendor specific objects can be used to access the different
memory areas. However, most applications requires only the standard DeviceNet objects.
For a complete description of the available objects, please refer to DeviceNet object
implementation on page 3–6.
D485 internal memory buffer
Assembly
object
(Not available on
The input and output areas can hold two types of data:
• I/O data: This data is sent/recevied upon change of value, polling or cyclically.
• Explicit data: This data is updated on request from another node on the fieldbus.
The amount of data that should be treated as I/O data is determined by the 'I/O Sizes'
parameter in the EnerVista P485/D485 Setup software. The remainder will be treated as
explicit data. By default (that is, when using 'automatic' I/O sizes), all data is treated as I/O
data.
Internal memory buffer
Input data
(up to 512 bytes)
Output data
(up to 512 bytes)
1024 bytes
Figure 3-2: Internal memory buffer
I/O data
Input data
Explicit data
I/O data
Output data
Explicit data
General data
the fieldbus)
Connection object
I/O connections
Figure 3-3: D485 memory structure
DATA EXCHANGE
Identity
object
Message router
object
DeviceNet
object
Explicit
messages
Link layer
DeviceNet network
3–3