Memory array built-in self-test circuit having a programmable pattern

Abstract

An ABIST circuit for testing a memory array has a blanket write subcycle (WC), an RC.sub.3 subcycle, and an RC.sub.4 subcycle. The ABIST circuit includes a programmable pattern generator that provides eight programmable data bits, eight programmable read/write bits, and two programmable address frequency bits to determine the specific test patterns applied to the memory array. The address frequency bits determine how many memory cycles will be performed on each cell of the memory array. In X1 mode, only one memory cycle is performed on each cell during any given subcycle. In X2 mode, two memory cycles are performed on each cell, allowing a cell to be written, then subsequently read in the same subcycle, In X4 mode, four memory cycles are performed on each cell, and in Xg mode, all eight bits of read/write and data are used on each cell, resulting in eight memory cycles for each cell within the memory array.