Keeping pace with a single - chip I 6 - bit

The emphasis in contemporary microprocessor development has been on 8-bit word lengths. Unfortunately, for many applications, the 8-bit microprocessor cannot provide the required accuracy, throughput, programming ease, or flexibility. The ntultichip 16-bit processor has been cost effective in many of these applications, but has provided unused flexibility or speed (at extra cost) in others. National Semiconductor has developed a singlechip 16-bit microprocessor, the Processing and Control Element (PACE), to provide the benefits of a 16-bit CPU with greater simplicity than the multi-chip design. The benefits accrue from integrating the functions of not only the multi-chip CPU, but also most of the functions that were previously implemented with TTL devices. In addition, a group of compatible microcomputer chips has been developed to augment the basic processor. A complete microcomputer system, with 1024 words (16,384 bits) of read-only program storage, clocks, buffers and one 16-bit or two 8-bit peripherals is shown in Figure 1. Table I lists features and benefits of this microprocessor.