Omron CQM1H-SCB41 operation manual Host Link Communications, Simultaneous Usage of Both Ports

Application Procedure Section 4-1

4-1-1 Host Link Communications

Connect One Computer to Multiple PCs

Computer Monitoring and Control of PCs

Redundant Error

Checking

Host Link communications are supported by all CQM1H-series CPU Units. A Serial Communications Board can be used to connect a single PC to more than one host computer for Host Link communications, including slave-initiated com- munications. Host Link communications provide the following features.

An RS-422A/485 port can be used to connect one host computer to up to 32 CQM1H-series PCs.

Host Link communications enable the host computer to monitor or control PC operations and to read and write I/O memory in the PCs.

Both vertical and horizontal (FCS) parity checks are performed on communica- tions data to achieve essentially error-free communications. Combining error checking and retry processing goes one step further to eliminate nearly all the effects of communications problems.

Simultaneous Usage of Both Ports

The Serial Communications Board provides two serial communications ports that can be used simultaneously to connect to two different networks of host computers in addition to the connections made directly from the built-in CPU Unit ports.

Slave-initiated Communications

Communications can be performed either by sending a command from a host and having the PC return a response, or by sending data from a PC to the host.

Note A Host Link connection can also be used to connect the PC to a Programming Device running on a personal computer. The following two modes can be used to connect to computers running Programming Devices. Only the Host Link Mode can be used for the Serial Communications Board.

Serial communications	Features
mode
Host Link	Functions as a communications protocol with standard
	host computers.
	Either 1:1 or 1:N connections are possible.
	Slower than a peripheral bus connection.
	Connection is possible through a modem or Optical Link
	Adapter, and long-distance and 1:N connections are
	possible using RS-422A/485.
Peripheral bus	Enables high-speed communications. A peripheral bus
	connection is thus the normal mode used to connect to a
	computer running the CX-Programmer.
	Only 1:1 connections are possible.
	With the CQM1H, the baud rate of the Programming
	Device is detected when the connection is made.

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