MC6829

@ MOTOROLA MC6829 Advance Infor:rnation MEMORY MANAGEMENT UNIT The principle function of the MC6829 Memory Management Unit (MMUI is to expand the address space of the MC6809 from 64K bytes to a maximum of 2 Megabytes. Each MMU is capable of handling four different concurrent tasks including DMA. The MMU can also protect the address space of one task from modification by another task. Memory address space expansion is accomplished by applying the upper five address lines of the processor (A 11-A151 along with the contents of a 5-bit task register to an internal high-speed mapping RAM. The MMU output consists of ten physical address lines (PA 11-PA201 which, when combined with the eleven lower address lines of the processor (AO-A101, forms a physical address space of 2 Megabytes. Each task is assigned memory in increments of 2K bytes up to a total of 64K bytes. In this manner, the address spaces of different tasks can be kept separate from one another. The resulting simplification of ...