Chapter 9. Modbus/TCP Client
170
PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual
GFK-2224Q
Monitoring the Communications Channel
The status data can be used to monitor communications and take action after certain events.
Monitoring the COMMREQ Status Word
It is critical to monitor the CRS word for each COMMREQ function. First, zero the associated CRS word before
executing the COMMREQ function. When the CRS word becomes non-zero, the Ethernet interface has updated
it. If the CRS word is updated to a one (1), the Command Block was processed successfully by the Ethernet
interface. If the CRS word is updated to a value other than 1, an error occurred in processing the Command
Block.
Do not use data received from a server until the CRS word for that channel is 1. In addition, do not initiate any
additional commands to a channel until the CRS word has been updated. The exception to this rule is when
you want to terminate a command by using the Close Modbus/TCP Connection command.
Monitoring the Channel Open Bit
This bit is 1 when a Channel has successfully established a connection with a remote server, and is 0 when a
Channel has been closed.. The Channel Open Bit is meaningful when the CPU is in Run mode and the
particular channel is being used by Modbus/TCP. The Channel Open Bit is set at the same time the successful
status is returned to the CRS word for the Open Modbus/TCP Connection COMMREQ.
Sequencing Communications Requests
If the Ethernet interface receives Command Blocks from the CPU faster than it can process them, the Ethernet
interface will log an exception event 08, Entry 2=0024H and will log the PLC Fault Table entry:
“Backplane Communications with PLC Fault; Lost Request”
Only one COMMREQ function per channel can be pending at one time. A COMMREQ function is pending from
the time it is initiated in the ladder program until its CRS word has been updated to a non-zero value by the
Ethernet interface.
Содержание PACSystems RX7i
Страница 45: ......
Страница 54: ...Chapter 4 Configuration GFK 2224Q January 2017 41 Figure 18 CPE400 Advanced Ethernet Configuration LAN1 LAN 2 ...
Страница 80: ...Chapter 4 Configuration GFK 2224Q January 2017 67 ...
Страница 81: ......
Страница 122: ...Chapter 6 Programming EGD Commands GFK 2224Q January 2017 109 ...
Страница 142: ...Chapter 7 Programming SRTP Channel Commands GFK 2224Q January 2017 129 Figure 51 Sample Ladder Logic for COMMREQ ...
Страница 147: ......
Страница 193: ...Chapter 10 OPC UA Server 180 PACSystems RX7i RX3i TCP IP Ethernet Communications User Manual GFK 2224Q Example ...
Страница 202: ...Chapter 10 OPC UA Server GFK 2224Q January 2017 189 Figure 73 Machine Edition Online Command to Set Passwords ...
Страница 211: ......
Страница 253: ...Chapter 12 Diagnostics 240 PACSystems RX7i RX3i TCP IP Ethernet Communications User Manual GFK 2224Q ...
Страница 262: ...Chapter 13 Network Administration GFK 2224Q January 2017 249 ...
Страница 263: ......