This work proposes in-situ Real-Time Error Detection (RTD): embedding hardware in a memory array for detecting a fault in the array when it occurs, rather than when it is read. RTD breaks the serialization between data access and error detection and, thus, it can speed-up the access-time of arrays that use in-line error-detection and correction. The approach can also reduce the time needed to root-cause array related bugs during post-silicon validation and product testing. The paper presents how to build RTD into an array with flip-flops to track in real-time the column-parity and introduces a two-dimensional RTD based error-correction scheme. As compared to SECDED, the evaluated scheme has comparable error-detection and correction strength and, depending on the array dimensions, the access time is reduced by 8-24% at an area and power overhead between 12-53% and 21-42% respectively.