When zenon variable has ALT_VAL status bit (bit 27) the Process Gateway iec870Slave sends value changes in ASDU with quality descriptor flag IV ('invalid') or NT ('not topical'). It should send, in quality descriptor in ASDU, the flag SB - 'substituted' like it does currently when zenon variable has status bit SB_870 (bit 45).
When zenon variable has ALT_VAL status bit (bit 27) the Process Gateway iec870Slave sends value changes in ASDU with quality descriptor flag IV ('invalid') or NT ('not topical'). It should send, in quality descriptor in ASDU, the flag SB - 'substituted' like it does currently when zenon variable has status bit SB_870 (bit 45).
zenon 'alternative value' status bit does no longer influence the 870-flag IV nor NT. The 870-flag SB is used instead.