Abstract: Read Only Memory (ROM) (10) data may be selectively inverted to decrease energy dissipation. Within the ROM (10), a plurality of memory cells (16) are connected to bit-line (18) and word-line (20) and store data, which determines the loading for a particular line. Line loading may be manipulated by accessing initial mapping information (23) of the ROM (10) and calculating the line loading on each line (18 or 20) and whenever a line's load exceeds a threshold, data stored in the memory cells (16) on the particular line (18 or 20) are inverted. Having done this, new mapping information (23) is produced and used to retrieve data from the ROM (10).

Abstract: A phase locked loop (PLL) (40) simultaneously has both relatively-low power consumption and relatively-low jitter on a clock output signal. The PLL (40) includes a phase detector (41) and a phase error accumulator (42) connected to the output of the phase detector (41). The phase error accumulator (42) samples an output of the phase detector (41) at a relatively-high clock rate, but accumulates these samples and provides an output thereof to a loop filter (43) at a relatively-low clock rate. Thus the PLL (40) captures short periods of phase delay to maintain low clock output signal jitter, while at the same time, however, the loop filter (43) need only adjust its output periodically, at the relatively-low rate, thereby saving power. The phase detector (41) detects a metastable condition on a phase detector latch (60) and resolves to an up pulse or a down pulse to further reduce clock output signal jitter.