Instruction Packet; Status Packet(Return Packet) - Robotis Dynamixel AX-12 User Manual

DYNAMIXEL

3-2. Instruction Packet

Instruction Packet
0XFF 0XFF
ID
Broadcasting ID
LENGTH
INSTRUCTION
PARAMETER0...N
CHECK SUM

3-3. Status Packet(Return Packet)

AX-12
The Instruction Packet is the packet sent by the main controller to the Dynamixel units
to send commands. The structure of the Instruction Packet is as the following.
OXFF 0XFF ID LENGTH INSTRUCTION PARAMETER1 ...PARAMETER N CHECK SUM
The meanings of each packet byte definition are as the following.
The two 0XFF bytes indicate the start of an incoming packet.
The unique ID of a Dynamixel unit. There are 254 available ID values, ranging from
0X00 to 0XFD.
ID 0XFE is the Broadcasting ID which indicates all of the connected Dynamixel units.
Packets sent with this ID apply to all Dynamixel units on the network. Thus packets sent
with a broadcasting ID will not return any status packets.
The length of the packet where its value is "Number of parameters (N) + 2"
The instruction for the Dynamixel actuator to perform.
Used if there is additional information needed to be sent other than the instruction itself.
The computation method for the 'Check Sum' is as the following.
Check Sum = ~ (ID + Length + Instruction + Parameter1 + ... Parameter N)
If the calculated value is larger than 255, the lower byte is defined as the checksum
value.
~ represents the NOT logic operation.
The Status Packet is the response packet from the Dynamixel units to the Main
Controller after receiving an instruction packet. The structure of the status packet is as
the following.
OXFF 0XFF ID LENGTH ERROR PARAMETER1 PARAMETER2...PARAMETER N CHECK SUM
10