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CONNECTION

Connection is made to the 9-pin female connector on the encoder circuit board. A standard 9-pin serial cable can be used to connect to the serial port of the host computer system. All other connections to the encoder circuit board remain the same.

COMMUNICATION PROTOCOL

The alarm communications consist of an individual byte for each alarm input sent to the alarm encoder. The serial input buffer has a capacity of 16 individual alarms. Alarms are contained in a first-in, first-out buffer (fifo) and sent out in the order that they are received into the buffer. The communications protocol consists of 9600 baud, 8 bits, no parity, and 1 stop bit. The operation for each alarm transmission is as follows:

• Host computer sends an RTS (request-to-send).
• The alarm encoder returns a CTS within 100 msec. maximum if the encoder input buffer is not full. The host program should contain a timeout of greater than 100 msec. A timeout of 1 second is recommended to avoid hangups.

          --Typical time to return CTS is 0-5msec.

• Host computer sends the alarm data byte
• --The alarm data byte consists of 8 bits:
•       The first bit is a status bit--
•           A zero in the first bit indicates the bbbbbbyte contains an alarm to be sent.
• --The next seven bits are the binary --number of the alarm input number. For --example,
•   00000111 indicates an alarm in zone 7
•   00001010 indicates an alarm in zone 10
• --If the first bit is a 1, a control instruction --is sent. For example,
•    If the first bit is a 1, followed by all blzeros, the input buffer is reset and all blalarm transmissions are aborted.