ZHCS103Q March 2011 – March 2024 TUSB7320 , TUSB7340
PRODUCTION DATA
To enable the serial-bus interface, a pullup resistor must be implemented on the SCL signal. At the rising edge of PERST# or GRST#, whichever occurs later in time, the SCL terminal is checked for a pullup resistor. If one is detected, then bit 3 (SBDETECT) in Serial Bus Control and Status Register) is set. Software may disable the serial-bus interface at any time by writing a 0b to the SBDETECT bit. If no external EEPROM is required, then the serial-bus interface is permanently disabled by attaching a pull-down resistor to the SCL signal.
The host controller implements a two-terminal serial interface with one clock signal (SCL) and one data signal (SDA). The SCL signal is an unidirectional output from the host controller and the SDA signal is bidirectional. Both are open-drain signals and require pullup resistors. The host controller is a bus controller device and drives SCL at approximately 60 kHz during data transfers and places SCL in a high-impedance state (0 frequency) during bus idle states. The serial EEPROM is a bus target device and must acknowledge a target address equal to A0h. Figure 6-2 illustrates an example application implementing the two-wire serial bus.