Futaba RS302CD - Manual (Page 13)

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Bit3 ~ Bit0：Address assignment of a return packet
(1) Data return from predetermined addresses
Setting the Bit3 through Bit0 like the table below when sending a short packet makes it
possible to receive the data of the specified addresses in the servo’s memory map. The Bit0
indicates whether to require a return packet (Bit0=1) or not (Bit0=0). Please refer to the
Table 4.1 Send packet flags (p.11) for setting these bits in sending short packets. The
RS485 half duplex communication, which is used to communicate with servos, does not
allow addressing more than one servo that can send a return packet. After requesting a
return packet, do not send next data until completing reception of the return packet.
Table 4.2 Address assignment of return packet
Bit 3 2 1 0 Function
0 0 0 0 No return packet
0 0 0 1 Return ACK/NACK packet
0 0 1 1 Return the data of the memory map No.00 ~ No.29
0 1 0 1 Return the data of the memory map No.30 ~ No.59
0 1 1 1 Return the data of the memory map No.20 ~ No.29
1 0 0 1 Return the data of the memory map No.42 ~ No.59
1 0 1 1 Return the data of the memory map No.30 ~ No.41
1 1 1 1
Return the specified number of bytes of data starting from the
specified address.
( 2) Data return from user-defined addresses
Setting the Bit3 through Bit0 to “1” and sending a short command with the starting ad-
dress whose data you want to receive, the length of data and the count=00H makes it possi-
ble to return the specified number of bytes of the data starting from the specified address.
Available addresses in the memory map are from No.00 to No.139 (00H~8BH).
Ex） Return the data in the memory map addresses from No.42 (2AH) through No.43
(2BH) of the ID1 servo.
Hdr ID Flg Adr Len Cnt Sum
(3) ACK/NAK Packet
If a servo receives a request of sending ACK the Flags being set at Bit0=1, Bit1=0,
Bit2=0 and Bit3=0, the servo send ACK.
The return packet is constituted by only one byte of data like bellow:
Return packet = 07H: “ACK”
FA AF 01 0F 2A 02 26 00