As it turns out the 19 bit Communication State can be important to application developers since for AIS types 1,2 (Class A) and 18 (Class B non "CS") the UTC Hour:Min for the position report is encoded in it.
In SetN2K... routines the default value of 0x07ffff seems incorrect.
For Class B "CS" transmissions where communication state selector flag is 1 the default value must be
1100000000000000110.
For Type 18 Class B (non "CS") and for Type 1, 2 the value should be ??? 0x0 seems to be a better default option although not clear from the docs.
For type 3 again 0x0 seems to a better option.
Type 1, 2, and 18 ( non CS) use SOTDMA transmissions and tables 18 and 19 apply for Communication State
type 3 uses ITDMA and table 20 applies.
As it turns out the 19 bit Communication State can be important to application developers since for AIS types 1,2 (Class A) and 18 (Class B non "CS") the UTC Hour:Min for the position report is encoded in it.
In SetN2K... routines the default value of 0x07ffff seems incorrect.
For Class B "CS" transmissions where communication state selector flag is 1 the default value must be 1100000000000000110.
For Type 18 Class B (non "CS") and for Type 1, 2 the value should be ??? 0x0 seems to be a better default option although not clear from the docs.
For type 3 again 0x0 seems to a better option.
Type 1, 2, and 18 ( non CS) use SOTDMA transmissions and tables 18 and 19 apply for Communication State type 3 uses ITDMA and table 20 applies.
Here is a link to the documentation.
https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1371-5-201402-I!!PDF-E.pdf
I will be applying fixes to code and will log a pull request when ready... Just thought I would document the issue here.
--Luis