TONR — On-Delay Timer
Structured Text on-delay timer function block. Uses FBD_TIMER; the ST equivalent of ladder TON.
TOFR — Off-Delay Timer
Structured Text off-delay timer function block. Uses FBD_TIMER; the ST equivalent of ladder TOF.
RTOR — Retentive Timer
Structured Text retentive timer function block. Uses FBD_TIMER; the ST equivalent of ladder RTO.
CTUD — Count Up / Down
Structured Text up/down counter function block. Uses FBD_COUNTER; combines the roles of ladder CTU and CTD.