Design considerations for high-density high-speed bipolar ROM

This paper presents a high-density high-speed cross-point bipolar ROM (XROM) design for control store applications. The cross-point architecture reduces the cell size up to 35% by sharing the word-line base contact in a silicided-base technology. Circuit simulations show that the performance impact due to the series base silicide resistance is insignificant. Data-dependent access-time skew inherent to the conventional bipolar ROM circuit is discussed, and an active pull-down bit-line discharge circuit technique to reduce the skew is described. The density and performance potential of the XROM in a 0.5 mu m bipolar technology are assessed.