SMC Networks 1560 user manual Special Precautions and hints, Timing

Appendix C — Peer Cop Example

Contents

This allows a coil to control a specific function in the drive. You could use bit manipulation instructions operating on word 40100 (such as MBIT), but it is far simpler to just assign coils to specific functions, and then move these coils into the Control Word. These coils are then moved into word 40100 using the simple instruction shown below:

enable -		- active
	00001
abort -		- error
	400110
		- success
	BKLM
	00001

Now the user may control specific functions by turning on and off these coils. For example, to start the drive, the user would turn on coil 15, which is block moved to word 40100, setting Modicon bit 15 on. Register 40100 is then transmitted over Modbus Plus via the Peer Cop to the 1560-MBP, which then turns on bit 1 in the drive control word, starting the drive. Inputs 100001-100016 may then be examined to observe feedback, such as run acknowledgment.

Note that by using this approach, the complexity is minimized by setting up a control structure (peercop) up front once, which may now be easily copied and duplicated. Also, additional drives may be very easily controlled by simply adding a few entries to the peercop tables and a block move to transfer bit states to the drive.

Special Precautions and hints

Timing

Because all parameters to and from the drive must pass through the SCANport, be careful about adding additional devices, such as the HIM module, when critical drive communication timing is required. While it does not affect the transfer of parameters, it does affect the throughput, which may cause unexpected problems in speed critical applications. Other devices placed on the network will affect the speed of the Modbus Plus network. Programming panels and operator interfaces can add significant network load. Nodes going online or off-line momentarily disrupt the token passing pattern. For critical drive control, a separate dedicated Modbus Plus network is recommended.

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