So, to set individual bits in a word, in order to optimize transmitting them from PLC to SCADA, I use 16 BYTE_TO_BIT blocks, each using only BYTE_TO_BIT output BIT0:
Byte_0 to BYTE_TO_BIT IN, resulting BYTE_TO_BIT BIT0 to %MW500.0
Byte_1 to BYTE_TO_BIT IN, resulting BYTE_TO_BIT BIT0 to %MW500.1
Byte_2 to BYTE_TO_BIT IN, resulting BYTE_TO_BIT BIT0 to %MW500.2
etc.
lengthy but seems workable, and couldn't use the direct addressing in a DFB.
(Need direct addressing to ensure contiguous addresses sent to SCADA)
Am assuming this will not write to the non-specified %MW500. bits.
Would love to test it but haven't got Simulator past "This isn't a valid PLC Address..." message yet; shutdown all AB RSlinx processes, set Windows Simple TCPIP to enabled.