Transmission Protocol - Savch SDA2 Series User Manual

7.3 Transmission Protocol

7.3.1 Message types
Communications are configured as the single master and multiple slaves method. The servo motor drive operates
as a slave.
The messages sent/received between the master and servo motor drive are classified into the two types below:
• Query: Messages transferred from the master to the servo motor drive
• Response message: Messages transferred from the servo motor drive to the master
Communications are started by a query from the master. Communications are not performed between the servo
motor drive.
7.3.2 Message fields
The data format is as follows for both the query from the master and the response message from the servo motor
drive.
Station No. 1byte
FC
1byte
(Function
code)
Variable
Information
length
16bit
CRC check
(2byte)
7.3.3 Function codes (FC)
The six types of FC below are supported:
Category
Data manipulation
Coil data manipulation
Maintenance
・0: Broadcast query to all servo motor drives.
(No response message is issued.)
・1-31: Query for each station number.
Self station numbers 1-31 are responded in the response messages from the
servo motor drive.
・Master: Specify an FC according to the processing that you wish to execute.
・Servo motor drive: Returns the specified FC.
(If the servo motor drive has not finished processing successfully, the
message is returned with the MSB of the FC set to 1.)· · Exceptional response
・Query/response message: Data are set according to the FC.
・An exceptional code (1 byte) is returned in the exceptional response from the
servo motor drive.
・Query/response message: CRC-16 is added to the bottom of the frame.
(L)
・The sender calculates CRC-16 for the data sent, add it to the bottom of the
frame, and send the frame.
・The receiver calculates CRC-16 of the received data. If the calculation
(H) results are not equal to the received CRC-16, an error occurs.
If an error is detected, no response message is returned.
FC
03h (3)
10h (16)
01h (1)
05h (5)
0Fh (15)
08h (8)
Function
Read out various data
Write in various data
Read out coil data
Write in single coil data
Write in coil data
Echo back
158
Broadcasting
Disabled
Enabled
Disabled
Enabled
Enabled
Disabled