Microprocessor with external memory.

摘要

A microprocessor is provided which is capable of executing synchronous accesses to an external memory whether the external memory is operating at the same frequency as the operating frequency of the microprocessor or whether the external memory is operating at a frequency which is one-half the microprocessor operating frequency. The microprocessor includes a rate control input for receiving a rate control signal having a first level indicative of the microprocessor frequency being equal to the external memory frequency or a second level indicative of the microprocessor frequency being twice the external memory frequency. A memory access control is coupled to the rate control input and is responsive to the rate control signal, an internal microprocessor clock, and the external memory clock for causing the microprocessor to access the external memory in synchronism with the external memory clock when the external memory frequency is either equal to the microprocessor frequency or is one-half the microprocessor frequency. <IMAGE>