6-2-2. ASCII Protocol
To select this communications protocol, XP must be set to 0.
It is possible to operate the Astat Plus from a host using standard ASCII characters. Two functions are available to be able to READ and
WRITE parameters.
Write Parameters to ASTAT Plus:
To write data into a parameter, the command format is the following:
Request from host :
:ssWxxxyyy
↵
↵↵
↵↵
Response from the ASTAT :
:ssWxxxyyy
↵
↵↵
↵↵
where
:
is a char to indicate the command start,
ss
is the station address,
xxx
(3 bytes needed) is the parameter number, and
yyy
(3 bytes needed) is the value to write into the parameter. The
↵
↵↵
↵↵
is the return key to indicate the command stop.
Note: the parameters modification is not allowed while the motor is operating.
Read Parameters from ASTAT Plus:
To read a parameter, the command format is the following:
Request from host :
:ssRxxx
↵
↵↵
↵↵
Response from the ASTAT :
:ssRxxxyyyyy
↵
↵↵
↵↵
where
:
is a char to indicate the command start,
ss
is the station address,
xxx
(3 bytes needed) is the parameter number, and
yyyyy
(5 chars response) is the value of the parameter. The
↵
↵↵
↵↵
is the return key to indicate the command stop.
Examples:
If we are trying to communicate with station 2:
- to start the unit, the command will be:
:02W060000
↵
↵↵
↵↵
- to stop the unit, the command will be:
:02W060001
↵
↵↵
↵↵
- to set the acceleration ramp time to 35sec., the command will be:
:02W005035
↵
↵↵
↵↵
- to know which overload curve is selected, the command will be:
:02R016
↵
↵↵
↵↵
; ( if, for instance the response is
:02R01600004
↵
↵↵
↵↵
,
this means that the overload curve selected is IEC class 10 ).
The Table shown in 6-2-5 provides a complete reference for the parameters that can be controlled by the serial interface.
6. Appendix
6-5
6-5
6-2-3. MODBUS RTU Protocol
Modbus RTU is an standard communication protocol. It is completely predefined, so any Modbus RTU master device will be able to send
and receive data from Astat Plus. To select this communications protocol, XP must be set to 1.
The communication begins with a master request which is answered by the slave (Astat Plus).
Each message from master to slave and viceversa is transmitted asynchronously as follows:
Quiet time
Slave Address
Function Code
Data Field
CRC
Quiet time
3.5 chars
0-247
1-24
N chars
2 chars
3.5 chars
It is required to give a different address to each slave. A Modbus master is able to handle up to 248 different addresses, but as address 0 is
reserved for broadcast commands, only 247 slaves are allowed. The CRC is an error detection code.
Although Modbus protocol defines up to 24 different functions, only 3 of them will be useful to Astat Plus:
- Read
- Write
- Read + Write
