LMX9830 Bluetooth™ Serial Port Module

11.0 Low Power Modes (Continued)The interface between host and LMX9830 is defined asdescribed in Figure 22.LMX9830LMX9830HostRTS#CTS#TXRXRTS#CTS#TXRXFigure 22. UART NULL modem connection11.2.2 Disabling the UART transport layerThe Host can disable the UART transport layer by sendingthe “Disable Transport Layer” Command. The LMX9830will empty its buffers, send the confirmation event and disableits UART interface. Afterwards the UART interface willbe reconfigured to wake up on a falling edge of the CTSpin.11.2.3 LMX9830 enabling the UART interfaceAs the Transport Layer can be disabled in any situation theLMX9830 must first make sure the transport layer isenabled before sending data to the host. Possible scenarioscan be incoming data or incoming link indicators. If theUART is not enabled the LMX9830 assumes that the Hostis sleeping and waking it up by activating RTS. To be ableto react on that Wake up, the host has to monitor the CTSpin.As soon as the host activates its RTS pin, the LMX9830 willfirst send a confirmation event and then start to transmitthe events.11.2.4 Enabling the UART transport layer from the hostIf the host needs to send data or commands to theLMX9830 while the UART Transport Layer is disabled itmust first assume that the LMX9830 is sleeping and wake itup using its RTS signal.When the LMX9830 detects the Wake-Up signal it activatesthe UART HW and acknowledges the Wake-Up signalby settings its RTS. Additionally the Wake up will beconfirmed by a confirmation event. When the Host hasreceived this “Transport Layer Enabled” event, theLMX9830 is ready to receive commands.33 www.national.com