The Microcontroller Idea Book - Jan Axelson's Lakeview Research

Chapter 6
Internal code memory consists of the 8052-BASIC’s ROM, which uses the addresses from
0 to 1FFFh.
External data memory beginning at 0 is also required. BASIC-52 reserves the first 512 bytes
for its own use, and it stores the current BASIC-52 user program immediately above this
area. The memory map allows a choice of using an 8K RAM from 0 to 1FFFh, or a 32K
RAM, which uses the entire area from 0 to 7FFFh. (The 8052 also has 256 bytes of internal
data memory, which the memory map doesn’t show.)
Two 8K blocks of combined code/data memory are reserved beginning at 8000h. As Chapter
4 showed, BASIC-52’s programming commands store programs in nonvolatile memory
beginning at this location.
For the input and output, or I/O, circuits described in this chapter, the memory map reserves
the top block of data memory, from E000h to FFFFh. I/O interfaces include connections to
buffers, latches, switches, displays, motors, or just about anything besides the system’s main
memory. The I/O circuits don’t have to use this block, but BASIC-52 encourages it, since
it clears external memory only up to E000h on bootup (unless you specify a lower value by
saving MTOP with a PROG3 command.)
Figure 6-1. Memory map for the 8052-BASIC system’s internal and external
data and program memory.
88 The Microcontroller Idea Book