Robotis RX-28 - Manual (Page 11)

DYNAMIXEL RX-28
3-2. Instruction Packet
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.
Instruction Packet OXFF 0XFF ID LENGTH INSTRUCTION PARAMETER1 …PARAMETER N CHECK SUM
The meanings of each packet byte definition are as the following.
0XFF 0XFF The two 0XFF bytes indicate the start of an incoming packet.
ID The unique ID of a Dynamixel unit. There are 254 available ID values, ranging from
0X00 to 0XFD.
Broadcasting ID 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.
LENGTH The length of the packet where its value is “Number of parameters (N) + 2”
INSTRUCTION The instruction for the Dynamixel actuator to perform.
PARAMETER0…N Used if there is additional information needed to be sent other than the instruction itself.
CHECK SUM 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.
3-3. Status Packet(Return Packet)
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
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