Table of Contents
Advertisement
1.3
Memory Organization
The memory partitioning of the XC800 microcontrollers is typical of the Harvard
architecture where data and program areas are held in separate memory space. The
on-chip peripheral units are accessed using an internal Special Function Register (SFR)
memory area that occupies 128 bytes of address, which can be mapped or paged to
increase the number of addressable SFRs.
A typical memory map of the code space consists of internal ROM/Flash, on-chip Boot
ROM, an on-chip XRAM and/or external memory. The memory map of the data space is
typical of the standard 8051 architecture: the internal data memory consists of 128 bytes
of directly addressable Internal RAM (IRAM), 128 bytes of indirect addressable IRAM
and an 'external' RAM (XRAM). External data memory may be supported outside of the
internal range.
Figure 1-1
a typical memory map in user mode.
Bank F
Bank E
Bank D
Bank C
Bank B
Bank A
Bank 9
Bank 8
Bank 7
Bank 6
Bank 5
Bank 4
Bank 3
Bank 2
Bank 1
XRAM
Boot ROM
Internal Memory
Code Space
Figure 1-1
XC800 Memory Space and Typical Memory Map in user mode
User's Manual, V 0.1
provides a general overview of the XC800 memory space and
F' FFFF
Bank F
H
F' 0000
H
E' FFFF
Bank E
H
E' 0000
H
D' FFFF
Bank D
H
D' 0000
H
C' FFFF
Bank C
H
C' 0000
H
B' FFFF
Bank B
H
B' 0000
H
A' FFFF
Bank A
H
A' 0000
H
9' FFFF
Bank 9
H
9' 0000
H
8' FFFF
Bank 8
H
8' 0000
H
7' FFFF
Bank 7
H
7' 0000
H
6' FFFF
Bank 6
H
6' 0000
H
5' FFFF
Bank 5
H
5' 0000
H
4' FFFF
Bank 4
H
4' 0000
H
3' FFFF
H
Bank 3
3' 0000
H
2' FFFF
Bank 2
H
2' 0000
H
1' FFFF
H
Bank 1
1' 0000
H
0' FFFF
H
XRAM
0' F000
H
Reserved
0' C000
H
Reserved
0' 0000
H
External Data Space
Notes:
! XC800 supports memory extension of up to 1 Mbyte
program memory and 1 Mbyte external data memory.
This is accomplished by sixteen 64K bank blocks. At any
one time, only one bank of the respective memory is
active.
! In case of implemented memory extension, an additional
extension stack RAM is added on-chip and located from
80
to FF
. This memory is not accessible by software.
H
H
! The smallest memory space without memory extension
is such that only Bank 0 is available.
! In general, the data space where the corresponding
code space is occupied by internal memory is reserved.
! If supported by available pins, external memory may be
located at regions not occupied by internal memory.
Program Memory : In general, #EA = 1 selects dynamic
fetch from internal and external program memory; #EA =
0 selects to always fetch from external program memory
instead of Internal Memory .
Data Memory : External data is accessed by the MOVX
instruction.
! This memory mapping is general for user mode. Refer to
respective user's manuals for exact mappings for
specific device.
Memory Extension
Stack Pointer
(MEXSP)
Extension Stack RAM
1-2
Fundamental Structure
Indirect
Direct
Address
Address
Special Function
Internal RAM
Registers
7F
H
Internal RAM
00
H
Internal Data Space
V 1.0, 2005-01
XC800
FF
H
80
H
Advertisement
Table of Contents
