Remote Processing CX-10 - Manual (Page 41)

Appendix A CX-10 Modbus Map
Appendix A Modbus Map Page 8
Register 4783 operating detail
Data returned from this register depends upon the CX-10 master/slave status at the moment. By default, the CX-10 is in
slave mode. The only way to enter master mode is by the PRINT #3 command. When executed in Basic, the board enters
the master mode.
Operation of register 4783 is described below based on the OS mode at the moment.
Register 4783 in slave mode
This is the default mode. No Basic interaction is necessary when the CX-10 is in slave mode. However, if your Basic code
will be entering the master mode, some slave conditions may be of interest.
Reading regiser 4783 in slave mode can return one of the following values (states):
4783 return value Description
0 Idle state - no activity. Waiting for data. Best time to enter master mode
16 Receiving data on COM3. Indicates incoming message. Do not enter master mode.
21 Data receive complete on COM3. Have received message and is processing it. Do not enter
master mode.
255 Invalid packet received (CRC Error). This is cleared when read or 100 milli-seconds after the
error is discovered. Next state will be a 0, so entering master mode is OK.
Register 4783 in master mode
This mode is entered by executing a PRINT #3 command in Basic. Two modbus function codes are supported: 3 and 16.
Function code 3 is a query while 16 is a write. PRINT #3 syntax depends upon the function code.
For either function code, the following state machine status is returned:
4783 return value Description
0 Idle - nothing in 4782 buffer.
1 Master is sending via PRINT #3.
2 Master send complete
3 Master waiting for response.
NOTE: If an error occurs, 4783 will transistionto one of the error codes below instead of
progressing to state 4 or 5
4 Master receiving response
5 Master receive response complete
Error codes
254 Time out - no response received. See register 4815 to change time out value
255 Invalid packet received (CRC error)
Many states, such as 1 and 2, may operate so fast that these values may never be returned.