Synchronous dram controller with memory access commands timed for

Abstract

For an synchronous dynamic access memory ('S-DRAM') system including a memory assembly with multiple memory units, data access commands are placed on a command bus at specific times to facilitate gapless data bus operation. After receipt of a first memory access request, a first memory access command is issued on the command bus to exchange a first data string having a first length with a first one of the memory units. Subsequently, receipt occurs of a second memory access request is to exchange a second data string, of a second length, with a second one of the memory units. A determination is made of an earliest possible time for placement of a second memory access command upon the command bus; this considers various factors, such as the first length, data bus availability, command bus availability, and any predetermined delay in placement of the first data string onto the data bus. Accordingly, the second memory access command is placed upon the command bus at the determined time. After the first data string leaves the data bus, any exchange of data between the first memory unit and the data bus may be prevented for a predetermined time.