| 摘要 |
PURPOSE:To secure the sampling time by an amount equal to 1.5 clocks by providing a mask control circuit to input a precharging clock and a mask signal and masking the precharge operation by an extent equal to one cycle. CONSTITUTION:The contents of a register 1 are held as they are until the sampling operation of a programmable logic array PLA part is through, i.e., until an output strobe signal becomes once active and then turned inactive. Meanwhile the precharging operation is carried out for a period, the inverse of phi1 when no precharge mask signal is transmitted. The precharge mask signal kept an an active low level, i.e., a waveform obtained at a point (a) is turned into that of a point (b) after passing through a half clock delay circuit 7. Therefore an output waveform that secures an AND between the precharge mask signal and a precharging clock phi1 is turned into a waveform of a point (c). Thus, a high level period by 1.5 clocks of the waveform of the point (c) is secured as the sampling time of the part 3 after the input data is decided. |
