L
With the bulk of email here, I seem to have missed the IEC data type examples - do they exist on the web somewhere as part of another project?
As for the preference of N7:99 or 4XXXX or ???, I agree fully with the comment that from a parser's standpoint there doesn't have to be any
difference between N:34 and N7:34 and 4X:34 and Glob_Int:34. N and N7 and 4X and Glob_Int all can be names hashed from some list of tables. Maybe N7 is easier for AB folks to work with. Maybe 4X is easier for Modbus folks etc. The only key here is for the programmers NOT to put any significance on (or attempt to parse) the name. If desired, users can use typing (like
szMessage and nLen in "C" programs) as a memory jogger, but it is their option.
Maybe an I/O driver may like to interpret N7 as "special" meaning - or must be able to map N, 4X, Glob_Int to N7, but I don't see any great advantage in trying to force such typing in the PLC kernel. Worst case when the table is
created besides a name we must include a Type ( "create table named "johny_boy" with type "N").
In fact, we could alias the table names so that N7:34 and 4X:34 and Glob_Int all refer to the same location, with each alias being used in the most appropriate place. So N7 could be the alias the AB I/O server uses to rd/wr the value from a remote device, and 4X is the alias the Modbus I/O server uses to rd/wr the value from a remote device, and Glob_Int may be used by the logic programmer.
Regards;
Lynn August Linse, Senior Product Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected] www.lantronix.com
Tel: (949)450-7272 Fax: (949)453-7132
_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
As for the preference of N7:99 or 4XXXX or ???, I agree fully with the comment that from a parser's standpoint there doesn't have to be any
difference between N:34 and N7:34 and 4X:34 and Glob_Int:34. N and N7 and 4X and Glob_Int all can be names hashed from some list of tables. Maybe N7 is easier for AB folks to work with. Maybe 4X is easier for Modbus folks etc. The only key here is for the programmers NOT to put any significance on (or attempt to parse) the name. If desired, users can use typing (like
szMessage and nLen in "C" programs) as a memory jogger, but it is their option.
Maybe an I/O driver may like to interpret N7 as "special" meaning - or must be able to map N, 4X, Glob_Int to N7, but I don't see any great advantage in trying to force such typing in the PLC kernel. Worst case when the table is
created besides a name we must include a Type ( "create table named "johny_boy" with type "N").
In fact, we could alias the table names so that N7:34 and 4X:34 and Glob_Int all refer to the same location, with each alias being used in the most appropriate place. So N7 could be the alias the AB I/O server uses to rd/wr the value from a remote device, and 4X is the alias the Modbus I/O server uses to rd/wr the value from a remote device, and Glob_Int may be used by the logic programmer.
Regards;
Lynn August Linse, Senior Product Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected] www.lantronix.com
Tel: (949)450-7272 Fax: (949)453-7132
_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
