A configurable cellular array is provided having a 2-dimensional array of cells in which each cell in the array has at least one input and output connection at least one bit wide to its neighbours. Each cell also has a programmable routing circuit to permit intercellular connections to be made. In one arrangement each cell contains a programmable function unit which includes a plurality of multiplexers. In a preferred arrangement the function unit and routing unit are programmable using associated Random Access Memory (RAM) areas within the cell. Each cell may be coupled to at least one global or array-crossing-signals so that all cells can be signalled simultaneously. The 2-dimensional array is rectangular and the intercell connections are orthogonal and are one bit wide.