Interface Solutions I2C-bus potx

10/2/2012 1 Interface Solutions I2C-bus Bipolar junction transistor PNP NPN 10/2/2012 2 Reduced models of the operation modes Modes of Operation 10/2/2012 3 Diode-Transistor Logic (DTL) NOR gate Diode-Transistor Logic (DTL) NAND gate Resistor-Transistor Logic (RTL) 10/2/2012 4 Sinking vs. Sourcing • 'Sink' means that the chip 'sinks' current down into itself. • 'Source' is just the reverse, the I/O pin is the actual source of the current. The LED will light when the PIC pin is low. The LED will light when the PIC pin is high. Sinking Input Sourcing Input Sinking Output Sourcing Output The current capacity of the PIC is of 25mA TTL Logic A Basic Output Open Collector Output Open Collectors with external pull-up. An open collector may be used with higher voltages Totem Pole Output Sinking / Sourcing ??? 10/2/2012 5 TTL logic NAND gate 7400 Sinking / Sourcing ??? Totem Pole Output ??? NOT Gate 7404 NAND Output Current Sinking & Sourcing Sinking Sourcing 10 10/2/2012 6 Open Collector Output Open Collectors with external pull-up. Tristate Gate 10/2/2012 7 Current Controlled vs Voltage Controlled Devices • JFET – Junction Field Effect Transistor • MOSFET – Metal Oxide Semiconductor Field Effect Transistor – D-MOSFET - Depletion Mode MOSFET – E- MOSFET - Enhancement Mode MOSFET Types of FET’s Types of Field Effect Transistors (The Classification) » JFET MOSFET (IGFET) n-Channel JFET p-Channel JFET n-Channel EMOSFET p-Channel EMOSFET Enhancement MOSFET Depletion MOSFET n-Channel DMOSFET p-Channel DMOSFET FET 10/2/2012 8 MOSFET circuit symbols CMOS Inverter 0V V DD CMOS Inverter Sinking / Sourcing ??? Totem Pole Output ??? 10/2/2012 9 AND gate Sinking / Sourcing ??? Totem Pole Output ??? OPEN-DRAIN (OPEN-COLLECTOR) OUTPUTS 10/2/2012 10 TRISTATE OUTPUTS Input/OutputVoltage Designations • VOL – the logic LOW output voltage. • VOH– the logic HIGH output voltage. • VIL – the logic LOW input voltage. • VIH – the logic HIGH input voltage. Input/Output Current Designations • IOL – the logic LOW output current. • IOH – the logic HIGH output current. • IIL – the logic LOW input current. • IIH – the logic HIGH input current. TTL Gate Sinking the Input Current from Two Gate Inputs TTL Gate Sourcing Current to Two Gate Inputs [...]... with voltages – But concerns on currents 11 10/2/2012 Interfacing Logic Families • CMOS to TTL High Sink Current for Driving 2 TTL Loads the negative value indicates current leaving the gate Interface Solutions I2C-bus 12 10/2/2012 Wired AND connection using diodes and a resistor 13 10/2/2012 MSB is fixed for all devices For Ex 1010 EPROM The addresses of most I2C devices are fixed and documented in... No - The basic arrangement for the LPT to I2C interface Mosfets Q1 & Q2 pull down the SCL & SDA lines for outgoing signals from the port, while the inverters interface the incoming SCL & SDA signals from the circuit under test PC-to-I2C (2) 21 10/2/2012 PC-to-I2C (2) PC-to-I2C (2) 22 10/2/2012 PC-to-I2C (2) PC-to-I2C (2) 23 10/2/2012 PC-to-I2C (2) I2C PC -interface http://www.pvv.org/~asgaut/i2c/i2c.html . 10/2/2012 1 Interface Solutions I2C-bus Bipolar junction transistor PNP NPN 10/2/2012 2 Reduced models. current leaving the gate High Sink Current for Driving 2 TTL Loads Interface Solutions I2C-bus 10/2/2012 13 Wired AND connection using diodes and a resistor 10/2/2012 14 The