C868_02 Datasheet, PDF (30/244 Pages) Infineon Technologies AG – 8 - Bit CMOS Microcontroller

C868
Memory Organization
3.3.2.1 Normal Mode
The normal mode is the standard 8051 compatible operating mode of the C800.
Table 3-2 Normal Memory Configuration for C868
Memory Space
Code Space
Internal Data Space
Memory Boundary
RAM/ROM: 0000_H to 1FFF_H
XRAM: FF00_H to FFFF_H
3.3.2.2 Bootstrap Mode
In the bootstrap mode, code is fetched from the boot-ROM when PC is less than 1000_H.
A dedicated 4 Kbyte boot-ROM is implemented to support this function. The actual code
inside the boot-ROM could be made up of various components such as programming
code for RAM module, download code, initialization routines or diagnostic software.
The bootstrap mode can be entered via one of the possible ways:
– hardware start-up sequence, or
– software entry using special unlock sequence
The exit from the bootstrap mode is possible via one of the possible ways:
– hardware reset, or
– software using special unlock sequence
The memory mapping for this mode is shown in the Table 3-3
Table 3-3 Bootstrap Memory Configuration for C868-1R
Memory Space
Code Space
Internal Data Space
Memory Boundary
Boot ROM: 0000_H to 0FFF_H
XRAM: FF00_H to FFFF_H, ROM/RAM: 0000_H to 1FFF_H
Once in the bootstrap mode, the on-chip XRAM is always enabled irrespective of the
XMAP0 bit in SFR SYSCON0. Exiting the bootstrap mode via software, the on-chip
XRAM access returns to the state prior to entering this mode, depending on XMAP0.
3.3.2.3 XRAM Modes
In the XRAM modes, code and data memory are swapped and in this case the code can
be fetched from the data space. This is useful for running diagnostic software.
The entry and exit into this mode is always through the special software unlock
sequence. The XRAM mode could be entered from either the normal mode or the
User’s Manual
3-6
V 0.4, 2002-01