LMX9820ASM NSC [National Semiconductor], LMX9820ASM Datasheet - Page 27

• Manufacturer Part Number: LMX9820ASM
• Description: Bluetooth Serial Port Module
• Manufacturer: NSC [National Semiconductor]

Revision 1.0
12.0 Command Interface
12.0 Command Interface
The LMX9820A offers Bluetooth functionality through
either a self-contained slave functionality or a simple com-
mand interface. The interface is carried over the UART
interface.
The following sections describe the protocol on the UART
interface between the LMX9820A and the host in com-
mand mode (see Figure 18). In Transparent mode, no data
framing is necessary and the device does not interpret data
carried over the interface as commands.
12.1 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 following
the model shown in Table 28.
12.1.1 Start and End Delimiters
The “STX” character is used as the start delimiter: STX =
0x02. ETX = 0x03 is used as the end delimiter.
.
0x52
‘R’
0x43
‘C’
0x69
‘i’
0x72
‘r’
Delimiter
1 Byte
Start
ID
REQUEST
(REQ)
Confirm
(CFM)
Indication
(IND)
Response
(RES)
- - - - - - - - - - - - - Checksum - - - - - - - - - - - - -
Direction
Type ID
Packet
1 Byte
Opcode
1 Byte
A request sent to the Bluetooth module.
All requests are answered by exactly one confirm.
The Bluetooth modules confirm to a request.
All requests are answered by exactly one confirm.
Information sent from the Bluetooth module that is not a direct confirm to a request.
Indicating status changes, incoming links, or unrequested events.
An optional response to an indication.
This is used to respond to some type of indication message.
(Continued)
LMX9820A
Table 29. Packet Type Identification
Figure 18. Bluetooth Functionality
Data Length
UART
Table 28. Packet Framing
2 Bytes
27
12.1.2 Packet Type ID
This byte identifies the type of packet. See Table 29 for
details.
12.1.3 Opcode
The opcode identifies the command to execute. The
opcode values can be found within the “LMX9820A Soft-
ware User’s Guide” included with the LMX9820A Evalua-
tion Board.
12.1.4 Data Length
Number of bytes in the Packet Data field. The maximum
size is 333 data bytes per packet.
12.1.5 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 check-
sum is 0x24).
Checksum
1 Byte
Description
UART
without Bluetooth™
<Data Length> Bytes
Existing device
capabilities
Packet Data
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Delimiter
1 Byte
End