IS220PRTDH1BC通用电气模块
关闭或重新分配通道有四种方式可以关闭或重新分配通道。
1.当PLC CPU停止时，所有正在使用的通道都会中止。
2.如果发生致命错误，通道将自动关闭。
3.可以通过发出中止通道命令来关闭通道（或所有通道）。
4.可以通过对信道号发出另一个命令来重新分配信道的任务。
这结束先前的信道操作并开始新的信道操作。发布通道命令的指南
确保PLC向FIP总线控制器发送命令块的速度不超过
总线控制器可以处理它们。如果发生这种情况，总线控制器将记录异常事件08，条目2=0024，并记录PLC故障表条目：“与PLC的背板通信故障；请求丢失”
对于每个通道，一次只能有一个COMREQ函数挂起。A.COMREQ函数从在程序中启动到其
FIP总线控制器已将COMREQ状态字更新为非零值。
应用程序应避免快速使用所有可用的TCP连接。
程序不应执行以下所有操作。
将重复次数设置为1，然后立即发出新的COMREQ前一个的完成。
将每个连续的COMREQ指向同一目标设备或同一信道数字
为避免使用所有TCP连接，设置重复次数（COMREQ字9）并将读/写周期（COMREQ字10和11）设置为非常大例如60秒。利用这些参数，程序将发出第一个COMREQ，
等待COMREQ状态（CRS）字变为1，等待COMREQ状态字变为1，以此类推。下图和文本解释了如何使用通信请求打开通信信道。该图具体说明了建立的操作读取通道命令。当PLC中的COMREQ功能有电力流时，通信请求开始。此时，命令块数据从PLC CPU发送到FIP总线控制器。
2.对于建立读通道命令，如果命令块无效，则立即返回COMREQ状态字。如果语法正确，状态词为在下一个重要事件后返回：无法正确建立通道并且及时地或在第一次成功传输数据时。
一旦通道成功设置，FIP总线控制器执行周期性按照命令块中的指定读取。
Closing or Re-tasking a Channel
There are four ways a channel can be closed or re-tasked.
1. When the PLC CPU is stopped, all channels in use are aborted.
2. A channel is automatically closed if a fatal error occurs.
3. A channel (or all channels) can be closed by issuing an Abort Channel command.
4. A channel can be re-tasked by issuing another command for its channel number.
This ends the previous channel operation and begins the new channel operation.
Guidelines for Issuing Channel Commands
Be sure the PLC does not send Command Blocks to the FIP Bus Controller faster than
the Bus Controller can process them. If that happens, the Bus Controller will log an exception event 08, Entry 2=0024 and log the PLC Fault Table entry:
“Backplane Communications with PLC Fault; Lost Request”
For each channel, there should be only one COMREQ function pending at a time. A
COMREQ function is pending from the time it is initiated in the program until its
COMREQ Status Word has been updated to a non-zero value by the FIP Bus Controller.
The application program should avoid quickly using up all available TCP connections.
The program should not do all the following.
Set the number of repetitions to 1 then issue a new COMREQ immediately upon
completion of the prior one.
Direct each successive COMREQ to the same target device or to the same channel
number.
To avoid using up all TCP connections, set the number of repetitions (COMREQ word 9)
to 2 and set the read/write period (COMREQ words 10 and 11) to be very large, for
example, 60 seconds. With these parameters the program will issue the first COMREQ,
wait for the COMREQ Status (CRS) word to turn to 1, then issue the next COMREQ,
wait for the COMREQ Status Word to turn to 1, and so forth.The figure and text below explain how a Communications Request is used to open a
communications channel. The figure specifically illustrates the operation of an Establish
Read Channel command.A Communications Request begins when there is power flow to a COMREQ function in the PLC. At this time, the Command Block data is sent from the PLC CPU to
the FIP Bus Controller.
2. For the Establish Read Channel command, the COMREQ Status word is returned immediately if the Command Block is invalid. If the syntax is correct, the status word is
returned after the next significant event: upon failure to establish a channel correctly
and in a timely manner or upon the first successful transfer of data.
Once the channel is successfully set up, the FIP Bus Controller performs the periodic
reads as specified in the Command Block.
