The HE693RTM705 is a Horner RTU/Modbus Master that can be controlled with Series 90-30 and 90-70 PCM based platforms. It provides two Modbus/RTU master channels that can access data from remote slaves of the RTU. Each channel of the module can be programmed individually for radio modem, dial-in, dial-out, multidrop, and direct connection operations. Both channels of the module can send or receive discrete or analog data through standard RTU commands. The operator can send multiple commands to each RTU slave with every command requesting a single point or multiple contiguous points of a maximum of 250 bytes. Data that is required to be sent is stored in the reference tables of the 90-30 or 90-70 Series modules. These reference data tables also store command lists that control what RTU commands need to be sent to slave RTUs. Once the HE693RTM705 starts, it uses these command lists to transfer data between slave RTUs and data tables of 90-30/90-70 Series modules. It may also run in a single command mode where the new commands are issued during the operation. The users can adjust the time between updates to each slave individually.

Each slave has an individual status field that can reflect the communication status of the RTU. By monitoring each status field continuously, the 90-30/90-70 modules can detect communication and configuration errors on a slave-by-slave basis. The HE693RTM705 Horner RTU/Modbus master module can support the report by exception when used with APG Modbus slaves. A slave connected to the module may originate a call to the master module when an exception occurs. The HE693RTM705 then determines the ID of the slave and executes the associated command list with a caller to send or receive the appropriate data.