3364940CSP2燃机电气模块
梯级#3：MOVEWORD函数将零移动到命令块中引用的COMREQ状态字（参见梯级4）。这将清除状态字。这个横档也是重置梯级#6中COMREQ功能块的FT输出线圈
状态字将被清除，COMREQ故障输出线圈将被清除启动COMREQ功能。
梯级#4-5：BLKMVINT函数设置COMREQ命令块内容。
激活这些梯级时，常量操作数将从指令中指示的地址开始移动到内存中。
第6级：COMREQ功能块有三个输入和两个输出参数。
输入字段指向命令块参数的起始位置在本例中为%R00301）。
SYSID字段定义接收命令数据的目标机架和插槽。这个SYSID的前两位数字（本例中为00）表示机架号，后两位数字（本例中为04）表示插槽编号。
任务字段指示用于指定机架和插槽的邮箱任务ID。
信道命令可以为0，网络诊断可以为2，或13（0Dh）通用消息。
如果存在以下情况，则FT输出（本例中为CMRQFLT）打开（设置为1）：阻止将命令块传递到FIP总线控制器的问题。在这种情况下，其他状态指示器不会更新该COMREQ。
本例中不使用OK输出，因此示例代码同样适用连接到90-70系列或90-30系列PLC。90-70系列PLC可维护多达32个单独的TCP/IP通信信道通过它可以与网络上的其他PLC或控制器交换数据。
本章说明如何使用COMREQ指令：
允许90-70系列PLC从指定范围内读取多达2048字节的数据网络上另一个PLC中的内存。
允许90-70系列PLC将多达2048字节的数据写入指定范围网络上另一个PLC中的内存。
允许90-70系列PLC向主机应用程序写入多达2048字节的数据网络。
使用信道状态位和详细信息监控通信信道频道状态字。
有关编程通信的更多一般说明，请参阅第6章请求FIP总线控制器并监控COMREQ状态。通信信道利用周期性数据传输的概念。本地PLC使用单个COMREQ建立与另一设备（PLC或控制器），并请求在它们之间周期性地传送特定数据。COMREQ的命令块指定传输的频率和方向以及要在传输中使用的存储器位置。
通道建立后，总线控制器自动管理建立通信和定期数据传输。
COMREQ指定通道是否在特定数量的转让（包括一次）或无限期转让。如果为特定号码设置了频道：
传输时，总线控制器将自动关闭通道转移已经发生。如果通道被设置为无限期保持打开，则以后可以关闭或重新分配任务。
Rung # 3: The MOVEWORD function moves a zero to the COMREQ Status Word referenced in the Command Block (see rung #4). This clears the status word. This rung also
resets the FT output coil of the COMREQ Function Block in rung #6. It is vital that the
status word be cleared and the COMREQ fault output coil be cleared each time before
initiating a COMREQ function.
Rungs # 4-5: The BLKMVINT functions set up the COMREQ Command Block contents.
When these rungs are activated, the constant operands are moved into memory beginning at the address indicated in the instruction.
Rung # 6: The COMREQ Function Block has three input and two output parameters.
The IN field points to the starting location of the Command Block parameters
(%R00301 in this example).
The SYSID field defines the target rack and slot to receive the command data. The
first two digits of SYSID (00 in this example) indicate the rack number, the last two
digits (04 in this example) indicate the slot number.
The TASK field indicates which mailbox task ID to use for the specified rack and slot.
It can be 0 for Channel commands, 2 for Network Diagnostics, or 13 (0Dh) for
Generic Messages.
The FT output (CMRQFLT in this example) is turned on (set to 1) if there were
problems preventing the delivery of the Command Block to the FIP Bus Controller.
In this case, the other status indicators are not updated for this COMREQ.
The OK output is not used in this example so that the sample code can equally apply
to a Series 90-70 or a Series 90-30 PLC.The Series 90-70 PLC can maintain up to 32 individual TCP/IP communications channels
through which it can exchange data with other PLCs or controllers on the network.
This chapter explains how to use COMREQ instructions to:
Allow the Series 90-70 PLC to read up to 2048 bytes of data from a specified range of
memory in another PLC on the network.
Allow the Series 90-70 PLC to write up to 2048 bytes of data into a specified range of
memory in another PLC on the network.
Allow the Series 90-70 PLC to write up to 2048 bytes of data to a host application on
the network.
Monitor communications channels using the Channel Status bits and the Detailed
Channel Status words.
See Chapter 6 for more general instructions about programming Communications
Requests to the FIP Bus Controller and monitoring COMREQ status.Communications channels utilize the concept of periodic data transfers. The local PLC
uses a single COMREQ to establish a channel (connection) to another device (PLC or
controller) and to request that specific data be periodically transferred between them.
The COMREQ’s Command Block specifies the frequency and direction of the transfer
and the memory locations to be used in the transfer.
After a channel is established, the Bus Controller automatically manages the
establishment of communications and the periodic data transfer.
The COMREQ specifies whether the channel will remain open for a specific number of
transfers (including just one), or indefinitely. If a channel is set up for a specific number
of transfer, the Bus Controller will close the channel automatically when that number of
transfers has taken place. If a channel is set up to remain open indefinitely, it can later be
closed or re-tasked.
