Intel’s BITBUS Protocol for Low-Cost Networking
Designed for cost-effective networking of distributed control systems, Intel’s BITBUS protocol is widely used in factory automation. BITBUS networks operate with one master and a maximum of 250 slaves. For detailed specifications, refer to Document No. 280645-001, Intel Corporation. The BITBUS specification adheres to a standard 9-way ‘D’ connector for designated connectors.
Differential BITBUS Transmission Detector
This circuit diagram illustrates a straightforward differential BITBUS transmission detector. Originally intended for monitoring BITBUS data presence between two control equipment pieces, this design serves a detection purpose.
Types of BITBUS Transmission
BITBUS specification supports two transmission types: synchronous and self-clocked. Synchronous transmission is ideal for high-speed data links (0.5 to 2 Mbits/sec) covering short distances (30 meters). These transmission methods provide flexibility based on speed and distance requirements.
BITBUS Data Transmission and Clocking
In BITBUS transmission, data and DATA signals are used, clocked through RTS and RTS signals. The self-clocked mode allows data transmission, albeit at a slower pace, covering longer distances – 375 Kbits/sec over 300 meters or 62.5 Kbits/sec over 1200 meters. Self-clocked mode merges serial data and the clock into a single signal through the data and data wire pair. IC2, a 74176 RS485 transceiver, is employed to detect BITBUS data.
Receiver Configuration and Data Detection
In this configuration, the IC2 operates exclusively in receiver mode. The DATA and DATA signal lines connect to pins 8 and 3 of the connectors respectively. The receiver output, found on pin 1, toggles when data is present on the BITBUS network. This activity is indicated by the flashing of two LEDs: the red LED signifies a High state, while the green LED represents a Low state.
Powering the BITBUS Monitor
If the network utilizes the full capabilities of the BITBUS system, the BITBUS Monitor can be powered using the +12 V supply line accessible on pin 1 and pin 6 of the BITBUS connector. The +12 V supply is stepped down to +5 V using IC1, a low-current regulator.
Ease of Use and Data Detection
Utilizing the BITBUS Monitor is remarkably straightforward. Connect the Monitor to the network, and the LEDs will flash when data is present. If the network is devoid of data, only one LED will illuminate, simplifying the process of data detection.