Computer system employing a bus conversion bridge for interfacing a master device residing on a multiplexed peripheral bus to a slave device residing on a split-address, split-data multiplexed peripheral bus

摘要

A multiple-transaction peripheral bus is provided with multiplexed address and data lines which is particularly adapted for portable applications. The multiple-transaction peripheral bus accommodates compatibility with existing hardware designs for a higher performance bus system with minimal conversion logic. A bus conversion bridge provides an interface between a 32-bit Peripheral Component Interconnect (PCI) bus and a 16-bit transaction Address/Data (A/D) which is associated with half the number of multiplexed address/data lines in comparison with the 32- bit PCI bus. The PCI bus accommodates data transfers between master and slave devices associated therewith, as does the narrower multiple- transaction A/D bus. The bus conversion bridge accommodates data transfers between the two buses, allowing a master device on one bus to communicate with a slave device on the other bus. The bus conversion bridge accomplishes this by 1) splitting both the 32- bit address/4-bit bus command and 32-bit data/4-bit byte enables received from the PCI bus during respective address and data phases into separate 16-bit/2-bit packets, and transmitting these packets over the multiple- transaction A/D bus during separate bus cycles, and 2) assembling multiple 16-bit address/2-bit bus command and multiple 16-bit data/2-bit byte enables received from the multiple-transaction A/D bus during separate bus cycles into single 32-bit/4-bit packets, and transmitting these packets over the PCI bus during respective address and data phases. Thus the bus conversion bridge allows a portable computer system with a narrower, 16- bit multiple-transaction A/D bus to communicate with peripherals on a wider, 32-bit PCI bus.