| 摘要 |
A carry chain includes a plurality of carry latches (20') which are disposed along a carry propagating line (12) to propagate a carry signal to a latch node (18). During precharge of the latch node (18), a precharge transistor (26') pulls the node to a logic one. During the precharge cycle, an N-channel transistor (34) which is a portion of the latch (20') is disconnected from the latch node (18) by a transistor (38). After the precharge cycle, this N-channel transistor (34) is reconnected to the latch node (18). This provides a low source impedance to quickly discharge the associated latch nodes (18) as the carry propagates along the carry chain (12).
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