1. ECE/CS-352: Embedded Microcontroller Systems The Silicon Laboratories C8051F020 Enhanced 8051 Part 1 External RAM

2. ECE/CS-352: Embedded Microcontroller Systems Memory Interface CPUMemory address data control

3. ECE/CS-352: Embedded Microcontroller Systems On-chip “External” RAM “external” RAM accessed with movx instruction Can add MORE memory Interfaced using External Data Memory Bus

4. ECE/CS-352: Embedded Microcontroller Systems Memory Expansion Can add more external RAM ports 5 and 6 implement address bus port 7 implements data bus port 4 implements control lines

5. ECE/CS-352: Embedded Microcontroller Systems Using External RAM Used to hold large data sets Accessed with movx instruction –MOVX A, @RiMove external data to A register –MOVX @Ri, AMove A to external data (8-bit address) –MOVX A, @DPTRMove external data (16-bit address) to A –MOVX @DPTR, AMove A to external data (16-bit address)

6. Points to Remember Remember that the data pointer can be incremented, but not decremented. Always remember to setup the DPTR with the location to be written to: –mov DPTR, #0100h If using a register Ri, only R0 or R1 can be used. ECE/CS-352: Embedded Microcontroller Systems