Abstract: A dynamic RAM memory refresh circuit is used with a microprocessor. In a small telecommunication switching system, a microprocessor shares access to memory with the dynamic RAM refresh circuit. Since circuitry size is of paramount importance, this circuit may be implemented with CMOS gate array technology. Since memory access is shared by the microprocessor and the dynamic RAM refresh circuit, processor through-put is affected. However, due to the speed of the dynamic RAM refresh circuit, the microprocessor real-time through-put is degraded only from 2 to 5 percent. A row of dynamic RAM memory is refreshed during each memory access by the refresh circuit, so that during a 2 millisecond inteval all dynamic RAM memory is refreshed. In addition, the dynamic RAM refresh circuit provides a strapping option to allow operation of the refresh circuit in conjunction with microprocessors of different clock frequency.

Abstract: This circuitry expands the memory addressing arrange of a microprocessor beyond its directly addressable memory capacity. This circuit uses the status outputs of the microprocessor to segregate memory accesses for program code instructions from accesses for other data. This segregation scheme assigns different memory banks to program code instructions and to data. Memory reads and writes for scratch pad data are performed from one bank of memory. Memory reads for program code instructions are performed from a separate memory bank. This memory bank technique can double the size of a microprocessor's directly addressable memory without changing the microprocessor's architecture. This circuitry is suitable for implementation with CMOS gate array technology.