In a magnetic random access memory (MRAM), numerous arrays of reference bit cells are coupled together by coupling their respective bit lines to a merged reference node. Pass gate circuitry coupled between the respective reference bit lines and the merged reference node is configured for selectively coupling or decoupling one or more of the reference bit lines to and from the merged reference node. The pass gate circuitry is controllable by programming one-time programmable devices coupled to the pass gate circuitry. The one-time programmable devices can be programmed to decouple flawed arrays of reference bit cells from the merged reference node or to select between redundant arrays of reference bit cells for coupling to the reference node.