LMX9820ASMX/NOPB National Semiconductor, LMX9820ASMX/NOPB Datasheet - Page 26

• Manufacturer Part Number: LMX9820ASMX/NOPB
• Description: MODULE BLUETOOTH SERIAL PORT SMD
• Manufacturer: National Semiconductor

Specifications of LMX9820ASMX/NOPB

• Frequency: 2.4GHz
• Data Rate - Maximum: 704kbps
• Modulation Or Protocol: Bluetooth v1.1, Class 2
• Applications: PDA's, POS Terminals
• Power - Output: 1dBm
• Sensitivity: -81dBm
• Voltage - Supply: 2.85 V ~ 3.6 V
• Current - Receiving: 65mA
• Current - Transmitting: 68mA
• Data Interface: PCB, Surface Mount
• Memory Size: 256Kb Flash
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 116-LTCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMX9820ASMX; LMX9820ASMXTR

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11.0 Power Reduction
11.2 UART TRANSPORT LAYER CONTROL
11.2.1 Hardware Wake-Up Functionality
In some circumstances, the host may switch off the trans-
port layer of the LMX9820A to reduce power consumption.
The host and LMX9820A then may shut down their UART
interfaces.
To simplify the system design, the UART interface is con-
figured for hardware wake-up functionality. For a detailed
timing and command functionality, see the “LMX9820A
Software Users Guide”.
The interface between the host and LMX9820A is shown in
Figure 19.
11.2.2 Disabling the UART Transport Layer
The host can disable the UART transport layer by sending
the “Disable Transport Layer” Command. The LMX9820A
will empty its buffers, send the confirmation event, and dis-
able its UART interface. The UART interface will then be
reconfigured to wake up the LMX9820A on a falling edge of
the CTS pin.
LMX9820A
Figure 19. UART Null Modem Connections
Host_WU
RTS#
CTS#
RX
TX
(optional)
(Continued)
RTS#
CTS#
TX
RX
GPIO
Host
26
11.2.3 LMX9820A Enabling the UART Interface
Because the transport layer can be disabled in any situa-
tion, the LMX9820A must verify that the transport layer is
enabled before sending data to the host. Possible situa-
tions in which the LMX9820A will need to re-enable the
interface include incoming data or incoming link indicators.
If the UART is not enabled, the LMX9820A must assume
that the host is in a low-power mode and initiate a wake-up
event by asserting RTS and setting HOST_WU to 1. To be
able to respond to the wake-up event, the host must moni-
tor its CTS input (i.e. the LMX9820A RTS output).
As soon as the host activates its RTS output (i.e. the
LMX9820A CTS input), the LMX9820A will first send a con-
firmation event and then start to transmit the events.
11.2.4 Enabling the UART Transport Layer from Host
If the host needs to send data or commands to the
LMX9820A while the UART transport layer is disabled, it
must first assume that the LMX9820A is sleeping and wake
it up by asserting the host RTS output (i.e. the LMX9820A
CTS input).
When the LMX9820A detects the wake-up signal, it
enables the UART and acknowledges the wake-up signal
by asserting its RTS output and HOST_WU signal. Addi-
tionally, the wake-up event will be acknowledged by send-
ing a confirmation event. When the host has received this
“Transport Layer Enabled” event, it knows the LMX9820A
is ready to receive commands.