LMX9830SM National Semiconductor, LMX9830SM Datasheet - Page 31

• Manufacturer Part Number: LMX9830SM
• Manufacturer: National Semiconductor

Specifications of LMX9830SM

• Lead Free Status / Rohs Status: Not Compliant

12.2 ENABLING AND DISABLING UART TRANSPORT
12.2.1 Hardware Wake up functionality
In certain usage scenarios the host is able to switch off the
transport layer of the LMX9830 in order to reduce power con-
sumption. Afterwards both devices, host and LMX9830 are
able to shut down their UART interfaces.
12.2.2 Disabling the UART Transport Layer
The Host can disable the UART transport layer by sending
the “Disable Transport Layer” Command. The LMX9830 will
empty its buffers, send the confirmation event and disable its
UART interface. Afterwards the UART interface will be re-
configured to wake up on a falling edge of the CTS pin.
12.2.3 LMX9830 Enabling the UART Interface
As the Transport Layer can be disabled in any situation the
LMX9830 must first make sure the transport layer is enabled
before sending data to the host. Possible scenarios can be
incoming data or incoming link indicators. If the UART is not
enabled the LMX9830 assumes that the Host is sleeping and
waking it up by activating RTS. To be able to react on that
Wake up, the host has to monitor the CTS pin.
As soon as the host activates its RTS pin, the LMX9830 will
first send a confirmation event and then start to transmit the
events.
12.2.4 Enabling the UART Transport Layer from the Host
If the host needs to send data or commands to the LMX9830
while the UART Transport Layer is disabled it must first as-
sume that the LMX9830 is sleeping and wake it up using its
RTS signal.
When the LMX9830 detects the Wake-Up signal it activates
the UART HW and acknowledges the Wake-Up signal by set-
tings its RTS. Additionally the Wake up will be confirmed by
a confirmation event. When the Host has received this “Trans-
port Layer Enabled” event, the LMX9830 is ready to receive
commands.
13.0 Command Interface
The LMX9830 offers Bluetooth functionality in either a self
contained slave functionality or over a simple command in-
terface. The interface is listening on the UART interface.
FIGURE 14. UART NULL Modem Connection
FIGURE 15. Bluetooth Functionality
31
In order to save system connections the UART interface is
reconfigured to hardware wakeup functionality. For a detailed
timing and command functionality please see also the
“LMX9830 Software User’s Guide”.
The interface between host and LMX9830 is defined as de-
scribed in Figure 14.
The following sections describe the protocol transported on
the UART interface between the LMX9830 and the host in
command mode (see Figure 15). In Transparent mode, no
data framing is necessary and the device does not listen for
commands.
13.1 FRAMING
The connection is considered “Error free”. But for packet
recognition and synchronization, some framing is used.
All packets sent in both directions are constructed per the
model shown in Table 24.
13.1.1 Start and End Delimiter
The “STX” char is used as start delimiter: STX = 0x02. ETX =
0x03 is used as end delimiter.
13.1.2 Packet Type ID
This byte identifies the type of packet. See Table 25 for de-
tails.
13.1.3 Opcode
The opcode identifies the command to execute. The opcode
values can be found within the “LMX9830 Software User’s
Guide” included within the LMX9830 Evaluation Board.
13.1.4 Data Length
Number of bytes in the Packet Data field. The maximum size
is defined with 333 data bytes per packet.
13.1.5 Checksum:
This is a simple Block Check Character (BCC) checksum of
the bytes “Packet type”, “Opcode” and “Data Length”. The
BCC checksum is calculated as low byte of the sum of all
bytes (e.g., if the sum of all bytes is 0x3724, the checksum is
0x24).
20180022
20180023
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