1. DIGITAL CONTROL INTERFACES MH0307 PLC & DATA ACQUISITION SYSTEMS DEPARTMENT OF MECHATRONICS ENGINEERING SRM UNIVERSITY

2. BUS Types of buses Based on Modularity – Stand-alone buses – Modular buses Based on nature of data transmission – Serial buses – Parallel buses Selection criteria Bandwidth Latency Cable length Ruggedness Ease of configuration Number of devices to be connected

3. 1. USB (Universal Serial Bus) New synchronous serial protocol for low to medium speed data transmission. Intended devices, – Keyboard – Mouse – Joystick – Digital camera – Speaker… Faster than RS232 (115+ kbps). Devices can be daisy chained.

4. Daisy Chaining of USB Devices Computer Device 1 Device 2 Device 3 USB Connection Out In USB Port

5. Features of USB Bandwidth 60 M Bps (Hi-speed). Latency 1000 μs (USB), 125 μs (Hi-speed). Range 5 m. Best setup and installation. Good connector ruggedness. Low cost. Hot plug and play.

6. Hot Plug-and-Play The ability to connect a device to the computer while a computer is in operation. As the device is connected, the OS would, – Recognize the device – Configure the device No manual intervention in the above process.

7. 2. IEEE 1394 Standard (Fire Wire) Very new introduction. Next level in serial communication after USB. Bandwidth is 400M bps or 50M Bps. In theory therefore, it can replace SCSI used for connecting hard disks. Fire Wire’s impact is most likely to be felt in multimedia applications involving audio and video.

8. 3. ETHERNET / LAN Mature technology – measurement systems, remote data storage, general networking, etc. IEEE standard 802.3. Data transfer rates, – 10 Mbps (10BASE-T) – 100 Mbps (100BASE-T)  Most common – 1 G bps (1000BASE-T). Also used for instrument control.

9. Features of Ethernet/LAN Bandwidth 12.5 M Bps (Fast), 125 M Bps (Gigabit). Latency 1000 μs (Fast, Gigabit). Range 100 m. Good setup and installation. Good connector ruggedness.

10. Advantages & Disadvantages Remote control Simplified instrument sharing Easy publication of data results Network administrators Actual transfer rates Inefficient data transfer Network overhead Security Additional measure to provide integrity and privacy

11. Parallel Communication Transmission of information over multiple links between two points. – Multiple electronic links Connecting devices such as an external mass storage device.

12. Parallel Transmission Multiple links

13. General Purpose Interface Bus (GPIB) GPIB – Formerly HPIB (Hewlett Packard). IEEE 488 – 8 bit Parallel port. Non-standard interfaces.

14. Features of GPIB Any instrument can be used. Up to 14 devices can be connected. Linear or star cable configuration – 24/25 wires – 3 types of connectors (Amphenol CHAMP or Cinch Series 57 MICRO RIBBON type) Bandwidth 1.8 M Bps (488.1), 8 M Bps (HS488). Latency 30 μs. Range 20 m, maximum 4 m per instrument. Good setup and installation. Best connector ruggedness.

15. Interface Signals and Lines Data bus (8 lines) similar to any computer data bus: commands/data Handshaking lines = asynchronous control of transfer on DIO Interface management lines = control of some interface functions