Omron SYSMAC C Series Operation Manual page 168

Data Exchange with CPU Unit
READ/WRIT Execution Restrictions
1, 2, 3...
Ladder Programming
Insert the WRIT instruction in a ladder program as follows:
• When the input conditions are met, a self-holding (latched) bit must used to
keep the execution condition ON until the WRIT instruction has been com-
pleted normally.
• While a WRIT instruction is being executed, a NC condition for the = Flag
(which turns ON when the WRIT instruction has completed normally) must be
used as an execution to prevent the next WRIT instruction from being execut-
ed.
Input
condition
(= Flag)
1. The differentiated READ and WRIT instructions cannot be executed for
Special I/O Units on SYSMAC BUS/2 Slave Racks. The READ and WRIT
instructions must be executed until the = Flag (A50006) turns ON indicating
that the execution is completed.
2. The READ and WRIT instructions cannot be simultaneously executed for
the same Special I/O Unit. In such cases, execute WRIT first, and after the
execution is completed, execute READ.
3. One SYSMAC BUS/2 Remote I/O Master Unit can simultaneously handle
up to two READ and WRIT instructions. If two READ and WRIT instructions
are executed for Units mounted to SYSMAC BUS/2 Slave Racks and an at-
tempt is made to execute a READ or WRIT instruction for a third Unit, the CY
Flag (A50004) will be turned ON without executing the third instruction.
4. Therefore, when continuously executing READ instructions, you can use
the READ and WRIT instructions for a maximum of two Special I/O Units
under each SYSMAC BUS/2 Remote I/O Master Unit.
5. Up to four SYSMAC BUS/2 Remote I/O Master Units can be mounted to the
CV1000 or CV2000. In this case, therefore, up to eight READ and WRIT in-
structions can be executed simultaneously.
6. Up to 255 words can be transferred using a READ or WRIT instruction.
Section 9-3
Self-holding
ON when WRIT is
completed normally
157