PAN1322Application Note 15 Revision 1.2, 2013-12-18Design GuideFigure 4. Host Initiates Low Power Mode Entry, eUniStone Initiates Exit1. The host allows eUniStone to enter low power mode2. eUniStone starts to enter low power mode3. When UARTRTS is high and P0.0 is low, eUniStone enters low power mode. The hostmay now enter low power mode by signaling UARTCTS high.4. The host enters low power mode.5. eUniStone wakes up and requests the host to wake up6. The host wakes up and accept UART data by lowering UARTCTS2.1.2 Hardware Flow ControlUse of the UART HW flow control pins UARTRTS and UARTCTS is strongly recommended.If the HW flow control is not used, UARTCTS must be tied low (flow "go"). Floating UARTCTS will resultin random stop of the UART flow.Without the HW flow control, a buffer overflow can occur on the UART, more probably at higher baudrate but also possible in lower baud rates due to congestion over the air.For the LPM protocol, UARTCTS shall be high during LPM. In some cases the module could send eventsbefore the host is completely awake. Therefore LPM shall not be used without HW flow control.2.2 EEPROM / I2C InterfaceAs shown in the block diagram (Figure 1), the eUniStone module is equipped with an EEPROM forstorage of the non-volatile information. The size of the EEPROM is 32 kbit.The EEPROM contains the following partitions: The Bluetooth Device Data (BD_DATA) Storage The application software Application specific data Production default valuesOn the PBA31309 module, the communication between the eBMU PMB 8754 and the EEPROM iscarried through a standard I2C bus. The I2C bus is also accessible from external pins, which is useful inthe development or debug phase in case the EEPROM gets corrupted.
