General Information
General Information
The CC1000 is a Modbus gateway for the Smart Lighting Control System D-Bus protocol. It can interface with a PC host
using either Ethernet or RS485 and communicates using the Modbus/RTU protocol.
The baud rate is fixed at 9600 bauds. The data format is 8 bits, no parity, 1 stop bit.
All numerical data is in integer form and must be scaled by multiplying/dividing with its associated unit to get the final
data value.
Reading is executed through function code 3. Writing is executed using function code 16. Most control is executed using
function code 5, but some may use function code 16 as well.
Function code 3 can support reading a single register or multiple registers at a time. When reading multiple registers, a
maximum of 125 registers (250 bytes) can be requested per command query. Requesting to read more than 125
registers at a time is considered an invalid command and will engender no response.
Function code 16 can write to a single register or multiple registers at a time. When writing to multiple registers, a
maximum of 4 registers (8 data bytes) can be written to at a time. Requesting to write more than 4 registers at a time is
considered an invalid command and will engender no response.
The CC1000 will not respond to an invalid command, this is to force the host PC doing the reading to time out. The
CC1000 has a typical response latency of 100 milliseconds, but as a safety margin, a latency of 300 milliseconds should
be allowed for, if this time is exceeded, the host PC should issue a time out.
An invalid command may be any one of the following:
1. The function code is not supported.
2. No register at the given register address for a given function code.
3. The data is malformed or out of range.
4. The CRC is incorrect.
The CC1000 can operate in two modes. The first mode is normal Modbus. The second mode is a variation of the
Modbus wherein any valid command will be executed but will not be responded to. The no response behavior for the
second mode is not an error but rather a normal behavior as required for certain types of applications.
CC1000 Modbus Reference 2.10e
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