[MC3031] - INV RS NAND LAT
The MC3031 implements a RS NAND latch with an inversed result for when both inputs are the same. Only the Q output is available. When the S (inverse "set") input exclusively goes high, the output (Q) goes high and stays high even if S goes low again. When the R (inverse "reset") input exclusively goes high, the output (Q) goes low and stays low even if R goes low again. If both go high at the same time, the output goes high. If both go low at the same time, the output does not change.
See MC3033 for a regular RS NAND latch.