Omron C120 System Manual page 48

Unit Number and I/O Word Allocation
I/O Link Unit Word
Settings
I/O Link Unit Words in
C200H Systems
Optical I/O Unit Word
Settings
Word Multipliers of
C1000H and C2000H
Setting Word Multipliers
34
An Expansion I/O Rack cannot be connected to a C500 Slave Rack via I/O Con-
necting Cable. Unlike C200H Slaves, C500 Slaves do not have switches for set-
ting output OFF/output hold during transmission error. All data is cleared from
C500 Slaves during transmission errors.
I/O Link Unit word settings determine which I/O words will be occupied by the
Unit. C120 and C500 I/O Link Units can be set to occupy 16 or 32 points. C20 I/O
Link Units always occupy 32 points. On C-series PCs there are 16 bits to a word,
so the I/O Link Unit will occupy either one or two words. Words 0 through 31 are
available. The actual words allocated in C200H, C1000H, and C2000H Sys-
tems will vary from the switch settings as described below. When setting words,
be sure not to set word numbers for one Unit which have already been set for
another Unit.
I/O Units mounted to Slave Racks are automatically assigned words according
to their mounting location. Words for all I/O Link Units must be set using their DIP
switches. For more details on settings, refer to 4-4 Switch Settings .
Although other PCs can be attached to the C200H through I/O Link Units, word
allocations for these Units are the same as those for Optical I/O Units, i.e., words
200 through 231. The actual words allocated the I/O Link Units will be 200
greater than the values set on the Units' switches.
Use the DIP switches on Optical I/O Units to set their I/O words. Do not combine
their input and output words into a single 16-point word. In other words, the two
8-point sections composing a single 16-point word must be either both input or
both output in all but C200H Systems. The actual Optical I/O Unit words in
C200H systems will be 200 greater than the values set on the Units' switches.
For more details on settings, refer to 4-4 Switch Settings .
The maximum number of bits a Master can transmit is 512 (32 words x 16 bits/
word). Words 0 to 31 can therefore be set for I/O Link Units and Optical I/O Units.
However, since the C1000H, and C2000H PCs can handle up to 2,048 bits (128
words x 16 bits/word), the Units cannot be assigned to words 32 to 127 of these
PCs without some identification other than the normal word settings. It is there-
fore necessary to assign numbers to the Masters to which I/O Link Units and Op-
tical I/O Units are connected and identify the words with these numbers as well
as the word settings.
These additionally assigned numbers, which can be from 0 through 3, are called
"word multipliers." The following equation illustrates the relationship between
word multipliers and word allocations.
I/O word allocation = (32 words x word multiplier) + (word set on Unit)
For example, suppose word 28 is set on an I/O Link Unit and word multiplier 2 is
assigned to the Master of that I/O Link Unit. The I/O word of the I/O Link Unit,
viewed from the PC, is computed as follows:
32 words x 2 + 28 words = word 92
A word multiplier does not have to be assigned to a Master to which only Slaves
are connected because word numbers will be automatically assigned by "free
location" to any I/O Units connected to the Slaves
The I/O words assigned to Optical I/O Units, Slaves, or I/O Link Units connected
to the Master with the lowest word multiplier must not be the same as the I/O
words assigned to the last I/O Unit.
The same word multiplier can be assigned to more than one Master. In this case,
however, the same word must not be set on the Units on a Master having the
same word multiplier as another Master.
Set the word multipliers in a C1000H or C2000H System using the Programming
Console as shown below. Before setting word multipliers, set the mode selector
Section 3-3