Exchanging Data With The Cpu Unit; Basic Communications Operations; Start And Stop Conditions For Remote I/O Communications; Communications Errors - Omron CS1W-CRM21 Operation Manual

Exchanging Data with the CPU Unit

5-1 Exchanging Data with the CPU Unit
5-1-1

Basic Communications Operations

5-1-2

Start and Stop Conditions for Remote I/O Communications

Note
5-1-3

Communications Errors

102
Communications for sharing data can be continuously performed between the
CPU Unit and Slave Units. This is called "remote I/O communications."
• Communications are started just by connecting the communications wir-
ing and turning ON the power (the communications power supply to the
Slave Unit and the power supply to the PLC), allowing data to be shared
between the I/O Memory Areas of the CPU Unit and the Slave Unit.
• The ladder program is used to read and write the areas where data is
shared (i.e., the areas allocated to Slave Units). When reading and writing
shared data, use the normal operation of the Slave Unit as a condition for
the read/write operation.
• Remote I/O communications start when power is turned ON to the PLC
and the Slave Unit communications power is turned ON. When the Regis-
tered Slave Unit Participation Standby Mode is enabled, however, remote
I/O communications will not start until all registered Slave Units are partic-
ipating.
• Remote I/O communications can also be started using a FINS command.
• If the I/O Communications Manual Startup Mode is set on the CX-Integra-
tor, the remote I/O communications will remain stopped even after the
power is turned ON. Remote I/O communications will not start until the
Remote I/O Communications Start Switch is turned ON in memory.
• In Communications Error Communications Stop Mode, all remote I/O
communications will be stopped if a communications error occurs in any
Slave Unit. When that happens, the Communications Error Communica-
tions Stop Flag (status bit 02) turns ON. The ESTP (Communications
Error Communications Stop Mode) DIP switch pin on the front of the
CompoNet Master Unit must be turned ON.
Communications will not stop for verification errors for registration tables or
duplicated Slave Unit address settings.
A communications error exists when a Slave Unit cannot return a normal
response to a communications request from a Master Unit. The following are
the main causes of communications errors:
• There is a malfunction at the Slave Unit itself.
• There is a disconnection in a communications cable to the Slave Unit.
• The communications power supply is OFF.
• The affected Slave Unit cannot receive correct data because of noise.
When a communication error occurs at a Slave Unit, the NS indicator on the
front of the Master Unit will light and d9 will be displayed on the seven-seg-
ment display. At the same time, the relevant Communications Error Flag (sta-
tus bit 00) will turn ON.
Section 5-1