Omron SYSMAC CV1000 User Manual

57
4-4 Sending Commands to Host Computers
Unlike the host interface on the CPU, a Host Link Unit has the right to start com-
munications. This means that the PC can send commands (i.e., SEND(192),
RECV(193), and CMND(194) instructions) to the host computer. Using this func-
tion, the PC can inform of the host computer of any error in operation. Therefore
the host computer does not need to communicate with the PC regularly, which
can reduce host computer overhead. Furthermore, a PC equipped with a SYS-
MAC NET Link Unit or SYSMAC LINK Unit can send commands to host comput-
ers connected to PCs on remote networks.
Note As a rule, communications initiated by Host Link Units should be used only when
a PC is connected 1-to-1 to a host computer. If a host computer is connected to
multiple PCs, simultaneous or overlapping transmissions from different PCs will
collide, preventing proper communications. If you need to used Host Link Unit-
initiated communications is a 1-to-N Host Link System, you will need to program
the PCs so that no two or more transmissions will interfere with each other.
4-4-1 Transfer of Right to Send
A Host Link Unit that has received a SEND(192), RECV(193), or CMND(194)
instruction from the PC has the right to send the command to the host computer.
After the Host Link Unit has sent the command and the host computer detects
the terminator of the command, the right to send will be transferred to the host
computer, and the host computer will return a response.
FCS
FCS
Node No.
Command block
Header
Text
Terminator
Node No.
Header
Text
Terminator
Right to send transferred
Response block
Host Link Unit
Host Computer
4-4-2 Commands from PC Instructions
The PC sends commands (SEND(192), RECV(193), and CMND(194) instruc-
tions) in the direction opposite to the normal direction of communications in the
Host Link System. Therefore, be aware of the following.
1, 2, 3... 1. SEND(192), RECV(193), and CMND(194) instructions sent by the PC are
converted into the CV-mode command format for network communications.
2. It is necessary to prepare a program to process the commands that the host
computer receives. Interrupt processing is used for the reception of a com-
mand, so the program must be prepared with care (refer to 3-6 Communica-
tions Timing).
Sending Commands to Host Computers Section 4-4

Omron SYSMAC CV1000 Specifications

General

Brand	Omron
Model	SYSMAC CV1000
Category	Controller
Language	English