Time-of-flight mass spectrometry utilizing a split memory

A spectrometer having a reduced memory size. The spectrometer has an address register, a detector for generating a digital measurement, first and second memories and an adder. The first memory stores data words having a value less than a maximum value, at the register defined address. The adder adds the data value on the data bus to the digital measurement to generate a sum value that is divided into a low order part having a value less or equal to the maximum value and an overflow value. The second memory stores at least a portion of the sum value at a location specified by the register value if the overflow value is greater than zero.