| IEC870-5-101 General The main serial interface port is, via a modem or direct used to provide an IEC60870-5-101 slave protocol functionality. The slave driver handles the reception of the requests from the master. When a error free request is received the slave driver will signal the B-CON application which is supposed to act on the request and send a response back to the master. This means that much of the IEC870-5-101 protocol is the responsibility of the B-CON application, which is free to define which requests it will support and the mapping of the information object addresses. However the B-CON language can in rare cases set some restriction on what kind of requests can be handled. The main port is configurable from 300 to 9600 baud, with fixed 8 data bit, even parity. The second serial port (port B, 6 pole RJ45 connector) is used for configuration of the RTU870 module using the IOTOOL32 Pro driver toolkit. The configuration of the second serial port is fixed, 9600 baud 8 data bit, none parity. Configuration via modem is not supported. The Modbus slave/node number on second serial port is fixed to 1. IEC60870-5-101 slave driver implementation Overview The IEC60870-5-101 slave driver is implemented as a separate task in the RTU firmware. The driver will operate at the main RS232 port of the Dallas 80C320 controller in the RTU. The driver occupies a number of BM registers. BM 30..33 are used for dial control, and BM38..BM49 are used to receive IEC60870-5-101 data buffers in control direction. The driver will use RX, TX, DCD and RTS (and GND) signals to communicate with a dialup modem or a null modem connection (e.g. industrial radio modem). If dialup mode is enabled, the driver activates the RTS signal permanently, and uses the DCD to determinate when a connection is established. When DCD is activated, the slave driver is ready to receive requests from the master station, no matter if the slave initiated the connection, or it is receiving an incoming call. If dialup mode is disabled, the DCD signal state is don't care, and RTS is activated according to the handshake option in the configuration menu. Communication sequence When connected, the RTU870 IEC60870-5-101 slave is typically scanned with one of the supported function codes in the control field: 0 SEND/CONFIRM expected Reset of remote link Returned answer • Single char frame E5 as acknowledge 3 SEND/CONFIRM expected User data Returned answers: • Single char frame E5 as acknowledge • Fixed length frame function codes 0=ACK or 1=NACK 9 REQUEST/RESPOND expected Request status of link Returned answers: • Fixed length frame function code 11=Status of link or access demand 10 REQUEST/RESPOND expected Request user data class 1 11 REQUEST/RESPOND expected Request user data class 2 Returned answers: • Single char frame E5 if no data available in either trans mit queue. • Fixed length frame function code 9=NACK if no data available in the requested transmit queue. • Variable length frame function code 8 with user data. |