Patent ID: 7546410

Claim:
A self timed memory chip having an apportionable data bus comprising: an array having an access timing; a self time unit configured to dynamically determine the access timing and to control a read access or a write access to the array according to the dynamic determination of the access timing, the self time unit further comprising: a ring oscillator having a frequency that tracks an access time of the array; and the ring oscillator further comprising a dynamically charged bit line; a shift register comprising a plurality of bits coupled to an output of the ring oscillator, and configured to shift responsive to the output of the ring oscillator; a decode coupled to one or more bits in the plurality of bits in the shift register, an output of the decode used to control the read access or the write access of the array; a data bus having “N bits”, the data bus consisting of: a first group of I/O signals having “M bits” configured to receive data to be stored into the memory chip; and a second group of I/O signals having “N-M bits” configured to drive data read from the memory chip; a third group of I/O signals having “M bits” configured to drive data received on the first group of I/O signals if the data received on the first group of I/O signals is not to be stored in the memory chip; a fourth group of I/O signals having “N-M bits” configured to receive data to be subsequently driven on the second group of I/O signals when the second group of I/O signals is available; wherein a value of “M” is programmable; wherein a clock frequency of the data bus is independent of the access timing of the array; and wherein the self timed memory chip is a dynamic random access memory (DRAM) chip.