The Tag Discrete Output block uses the status of the PLC signal parameters to determine the status of the associated control tag parameter. If the block does not receive a signal parameter value from the PLC, the block sets the associated block parameter to BadNot SpecificNotLimited. If the status of the Out PLC tag parameter (which is mapped to the TAGDO block OUT_D parameter) is bad, the block sets the value of the BLOCK_ERR parameter to Bad PV.