IS230SNRTH2A燃机通用电气卡件
建立到另一个PLC的读取通道使用“建立读取通道”命令打开与远程PLC并从该PLC读取数据。
如下面的示例所示，命令块指定周期、数量从远程PLC读取以执行，以及等待每个转移到完成。第一次读取立即执行，而不考虑时间段明确规定。
示例：建立读取通道命令块该示例命令块在IP上建立到远程PLC的通道（通道5）
地址3.0.0.1。它将COMREQ状态字返回到%R10。成功后执行命令后，总线控制器将读取“远程”PLC寄存器%R50-%R57进入“本地”PLC寄存器%R100-%R107。此通信将以7秒间隔重复10次。每次读取的超时时间为500ms。命令块定义
（字7）信道命令号：字7（02003十进制或07D3十六进制）请求可以设置读取通道。
（字8）通道号：字8指定用于读取的通道。这个值必须在1到32的范围内。如果信道超出范围，则命令错误指示为置于COMREQ状态字中。如果频道号与频道号相同已在使用中的通道将重新设置为执行此新命令。
（Word 9）读取重复次数：Word 9指定要执行的读取次数然后自动关闭通道。如果该值设置为1，则只有一次读取发布。如果此值设置为0，则在请求的时间段内发出读取，直到通道中止。
（字10）读取期间的时间单位：字10是指定时间单位的数字读取期间：秒
3秒
4分钟
5小时
（字11）读取周期的时间单位数：字11指定时间数
读取期间的单位
即使通道命令设置为发出单个读取。
示例读取周期：如果字10包含值3，则将秒指定为如果时间单位和字11包含值20，则读取周期为20秒。
通常在每个读取周期开始时发出读取。如果挂起的读取传输是读取期间未完成，信道错误位和详细信道状态字被设置为指示非致命周期错误。如果时间单位数为设置为零，则在上一次传输完成后立即发出后续传输，否发生错误的时间段。在期间错误发生后，挂起的传输仍然可以完成。
对于设置为发出多次读取的通道命令，将发出下一次读取传输仅在挂起的读取传输完成之后。
设置为发出单个读取的通道命令只能有一个挂起读取转移
（字12）每次读取的超时：字12指定时间（以第二）FIP总线控制器在设置
通道错误位和详细的通道状态字，用于指示非致命超时错误即使发生超时，传输仍然可以完成。因此应用程序可以选择如果
Establish a Read Channel to Another PLC
Use the Establish Read Channel Command to open a communications channel to a
remote PLC and to read data from that PLC.
As shown in the example below, the Command Block specifies the period, the number of
reads from the remote PLC to perform, and the timeout allowed in waiting for each
transfer to complete. The first read is performed immediately, regardless of the period
specified.
Example Establish Read Channel Command Block
This example command block establishes a channel (channel 5) to a remote PLC at IP
address 3.0.0.1. It returns the COMREQ Status Word to %R10. Following successful
execution of the command, the Bus Controller will read “remote” PLC registers
%R50-%R57 into “local” PLC registers %R100-%R107. This communication will be
repeated 10 times at 7 second intervals. The timeout period is 500 ms for each read.Command Block Definitions
(Word 7) Channel Command Number: Word 7 (02003 decimal or 07D3 hex) requests that
a read channel be set up.
(Word 8) Channel Number: Word 8 specifies the channel to be used for the read. This value
must be in the range of 1 to 32. If the channel is out of range, a command error indication is
placed in the COMREQ Status word. If the channel number is the same as a channel
already in use, the channel is retasked to perform this new command.
(Word 9) Number of Read Repetitions: Word 9 specifies the number of reads to perform
before automatically closing the channel. If this value is set to 1, only a single read is
issued. If this value is set to 0, reads are issued on the requested period until the channel
is aborted.
(Word 10) Time Units for Read Period: Words 10 is a number that specifies the time units
for the read period:econds
3 seconds
4 minutes
5 hours
(Word 11) Number of Time Units for Read Period: Word 11 specifies the number of time
units for the read period. The read period is in effect even when the channel command
is set up to issue a single read.
Example Read Period: If Word 10 contains a value of 3 specifying seconds as the
time unit and Word 11 contains a value of 20, then the read period is 20 seconds.
A read is normally issued at the start of each read period. If the pending read transfer is
not completed during the read period, the Channel Error bit and Detailed Channel
Status words are set to indicate a non-fatal period error. If the Number of Time Units is
set to zero, a subsequent transfer is issued as soon as the previous transfer completes, no
period errors occur.
A pending transfer can still complete after the period error occurs.
For channel commands set up to issue multiple reads, the next read transfer is issued
only after the pending read transfer completes.
A channel command set up to issue a single read can have only one pending read
transfer.
(Word 12) Timeout for Each Read: Word 12 specifies the time (in hundredths of a
second) the FIP Bus Controller waits for a read transfer to complete before setting the
Channel Error bit and Detailed Channel Status words to indicate a non-fatal timeout
error. The transfer can still complete even after a timeout occurs. As a result, an
application can choose what to do if one
