Allocating I/O - Omron DEVICENET#05-2003 Operation Manual

Functions
Error Processing
1-2-3

Allocating I/O

Fixed Allocation
Remote I/O communications with the DeviceNet Master Unit are carried out
by a MULTIPLE I/O TERMINAL based on the registered configuration. When
the power to the Communications Unit is turned ON, the bits allocated to the I/
O Units can be used to check the status (bits 0 to 7 of the first word) of the
Communications Unit.
Communica-
tions Unit
Note 1. If the configuration of the I/O Units is to be changed, a number of precau-
tions must be noted. For details, see 1-2-5 I/O Configuration Changes.
2. For details of data exchange timing, see 6-1-1 I/O Response Time.
Even if an error occurs in the I/O Unit interface after initialization is completed,
DeviceNet communications will continue normally. Therefore, an error pro-
cessing program section must be included in the CPU Unit to check the status
of the Communications Unit for errors that have occurred and to identify the
error type and location.
This section explains how words for a MULTIPLE I/O TERMINAL are allo-
cated in the output area and input area of the Master. For details of remote I/O
functions in the output area and input area of the Master such as word specifi-
cation, fixed allocation, and user-set allocation, refer to the DeviceNet Opera-
tion Manual (W267).
The output area and input area corresponding to the Communications Unit
node number for a MULTIPLE I/O TERMINAL are as shown in the following
diagram.
Output Area
The output area contains output bits in the order that I/O Units are connected
on the I/O Unit interface.
Input Area
The input area contains the Communications Unit status (two words), and
input bits in the order that I/O Units are connected on the I/O Unit interface.
Area corresponding to
Communications Unit
node number
The input and output bits for the I/O Unit interface are allocated in the
DeviceNet input and output areas in 16-point (one word) increments. With 8-
point I/O Units, these bits are allocated using the rightmost byte (bits 0 to 7),
and the leftmost byte (bits 8 to 15) will be 00 Hex.
DeviceNet Network
I/O Unit I/O Unit
Automatically recognizes the configuration of the
I/O Units
At startup
Communications with the DeviceNet Master Unit
based on this I/O configuration
Output area
Output bits on
the I/O Unit
interface
Section 1-2
I/O Unit
Input area
I/O Unit interface
status
Input bits on the I/O
Unit interface
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