6. Appendix
6-6
Read Parameters from ASTAT Plus
The function code assigned to Read is 3 (3h).
The request message from master must contain the following information:
- Slave address: the master must indicate which slave has been selected. The non-addressed slaves will receive the message but will
not execute the command. Only the slave with the corresponding address will send a response message.
- Function code: as related above, Read command is number 3.
- Data Field: as this is a read command, the data requested is the number of parameters to be read and the starting address to begin
to read.
Quiet time
Slave Address
Function Code
Data Field
CRC
Quiet time
starting address
3.5 chars
slave #
3
# of parameters
2 chars
3.5 chars
The response from the Astat Plus will contain the same slave address and function code, but the data field will include the total number
of chars read, and the value of the requested parameters.
Quiet time
Slave Address
Function Code
Data Field
CRC
Quiet time
# of chars read
3.5 chars
slave #
3
parameters value
2 chars
3.5 chars
Write Parameters to ASTAT Plus
The function code assigned to Write is 16 (10h).
The request message from master must contain the following information:
- Slave address: the master must indicate which slave has been selected. The non-addressed slaves will receive the message but will
not execute the command. Only the slave with the corresponding address will send a response message.
- Function code: as related above, Write command is number 10h.
- Data Field: as this is a write command, the data requested is the number of parameters to be written, number of chars, starting
address and the value to write.
Quiet time
Slave Address
Function Code
Data Field
CRC
Quiet time
starting address
3.5 chars
slave #
10
# of parameters
2 chars
3.5 chars
# of chars
values to write
The response from the Astat Plus will contain the same slave address and function code, but the data field will include the total number
of chars read, and the value of the requested parameters.
Quiet time
Slave Address
Function Code
Data Field
CRC Quiet time
starting address
3.5 chars
slave #
10
# of parameters
2 chars
3.5 chars
Read + Write Parameters to ASTAT Plus
The function code assigned to Read and Write is 23 (17h).
The request message from master must contain information to perform both operations:
- Slave address: the master must indicate which slave has been selected. The non-addressed slaves will receive the message but will
not execute the command. Only the slave with the corresponding address will send a response message.
- Function code: as related above, Write command is number 17h.
- Data Field: as a read command, the data requested is the starting address, and the quantity to read. As this is also a write command,
the data requested is the number of parameters to be written, number of chars, starting address and the value to write.
