DATX110 3BSC980004R784 control card 

DATX 110

A server device can, however, be forced into 'Listen Only Mode' in which it will monitor the messages on the communications system but not respond to them. This can affect the outcome of your application program if it depends upon any further exchange of data with the remote device. Generally, the mode is forced to remove a malfunctioning remote device from the communications system. The following diagnostic functions are dedicated to serial line devices. The normal response to the Return Query Data request is to loopback the same data. The function code and sub-function codes are also echoed.00 Return Query Data The data passed in the request data field is to be returned (looped back) in the response. The entire response message should be identical to the request.

Example and state diagram

 Here is an example of a request to remote device to Return Query Data. This uses a sub-function code of zero (00 00 hex in the two-byte field). The data to be returned is sent in the two-byte data field (A5 37 hex).

The data fields in responses to other kinds of queries could contain error counts or other data requested by the sub-function code 

The writing of coils via Modbus function 15 will be accomplished regardless of whether the addressed coils are disabled or not. Coils that are unprogrammed in the controller logic program are not automatically cleared upon power up. Thus, if such a coil is set ON by function code 15 and (even months later) an output is connected to that coil, the output will be hot.

Force Multiple Coils

This message forces each coil in a consecutive block of coils to a desired ON or OFF state. Any coil that exists within the controller can be forced to either state (ON or OFF). However, because the controller is actively scanning, unless the coils are disabled, the controller can also alter the state of the coil. Coils are numbered from zero (coil 00001 = zero, coil 00002 = one, and so on). The desired status of each coil is packed in the data field, one bit for each coil (1= ON, 0= OFF). The use of Slave address 0 (Broadcast Mode) will force all attached Slaves to modify the desired coils