The PAX PROFIBUS-DP Communications Option Card provides a direct connection for a PAX panel meter to a PROFIBUS-DP Network. This allows a PROFIBUS Master device, such as a PLC, to control and monitor the operation of the PAX meter. The meter functions as an intelligent PROFIBUS-DP Slave device on the Network.

The PROFIBUS-DP Network connects through a 9-pin D-subminiature female connector on the rear of the card. The card is installed in the PAX meter using a slotted rear cover, allowing the PROFIBUS-DP Connector to extend beyond the rear of the PAX case. Power for the card is provided internally from the power supply of the PAX meter. The PROFIBUS-DP Network is isolated from the control electronics on the card using high-speed optocouplers.

This fully featured communications card supports Automatic Baud Rate Detection, with an operating range of 9.6 Kbaud up to 12 Mbaud. The Station Address is set via rotary switches. The card's address is read at power up.

Data Exchange with the Master device occurs through cyclic I/O data transmission. The size of the I/O data block is determined by the selection of pre-configured Modules for Analog or Digital PAX meter type. All data values are in 32-bit integer format, Motorola byte ordering. The PROFIBUS-DP protocol per EN 50170 is implemented using the Siemens SPC3 ASIC. Three on-board Diagnostic LEDs indicate the status of Data Exchange (DATA), the SPC3 Watchdog (WD) and DP State Machine (DP).