Setting the Parameter
You can select `No' or `Yes' for the Modem Booster parameter at any serial port. he parameter will have the following effect:
If you select `No' for this parameter, incoming commands with function code 126 or 13 are passed directly to the slave device at the port. If the command is function code 126, the slave response will be returned to the originator of the Modbus command after the slave has completed the requested action, or when it returns an exception response indicating that it cannot complete the action.
electing `Yes' causes the second type of response (function code 13) to be used. If the command specifies function code 126, the BM85 will perform a conversion to function code 13 before sending the command to the slave device. he BM85 will then automatically handle the polling of the slave device until the command action is completed. It will return the final response to the originator of the command. he polling process is handled by the BM85 transparently to the originator.
Modem Booster Example
A P230 programming panel connected to a Modbus Plus networked controller can access a slave controller that is part of a Modbus network at a BM85 port. he P230 panel can remotely interrogate, program, and start the slave controller.
If the Modem Booster parameter is set, the P230 can issue a command with function code 126. he BM85 converts the function code and sends the converted command to the slave. he BM85 then handles polling of the slave, returning a response to the P230 when the slave device's action is completed.
o the originating device, the response appears as the one from the slave for function code 126. During this time, however, normal network transactions can continue between other devices in the user application and the other slave devices on the BM85 port's Modbus network.
Not:or Modicon 584 ontrollrs he Modem Booster will not function with 584 controllers that are in AFE84 mode. Function code 13 is not recognized by those controllers in that mode. You should select the Modem Booster `No' option for a BM85 port that will have 584 controllers connected to that port's Modbus network.
31007492 | Configuring the Modbus Models 35 |