Futaba RS302CD - Manual (Page 10)

10
4.CONTROL METHOD
Abstract
● Communication Protocol
The communication protocol of the RS301CR/RS302CD servo is based on RS485
(IEEE485) half duplex communication. Data transmission and reception are carried out
alternatively on the same signal line.
Normally, the RS301CR/RS302CD servo stands by in reception mode. But, when it
receives from RPU-10 a command to send the servo’s data and status, it switches to
transmission mode, sends them out and finally returns to reception mode.
● Memory Map
The RS301CR/RS302C servo has its own memory area to store data necessary for its
movement. This memory area is called “Memory Map”.
This memory map is divided into two groups. One is “RAM area” in which data will be
erased when the power is turned off. The other one is “ROM area” in which data is held
even after the power is turned off.
● Servo ID
You can set ID numbers to RS301CR/RS302C servos individually.
These ID numbers are used to identify servos during communication. The default
number of every servo is set to “1”. When you use multiple servos in a single
communication network, give them different ID numbers.
● Packet
A packet is a block that is used for sending a command to or receiving data from
RS301CR/RS302C servos. Packets are divided into the following three groups, having
different formats.
(1) Short Packet(→p.11)
Short packets are used for sending the data in the memory map toward a single servo.
(2) Long Packet(→p.14)
Long packets are used for sending the data in the memory map toward multiple servos
simultaneously.
(3) Return Packet(→p.16)
This is a packet that is sent from a servo when a return packet is requested.