UM012811-0904
Address
Space
eZ8 CPU
User Manual
18
and data. Program Memory is accessed using opcode fetches, operand fetches, and LDC/
LDCI instructions. Table 7 provides an example of a Program Memory map for a eZ8
CPU product with 64KB of Program Memory and 16 interrupt vectors.
Individual products containing the eZ8 CPU support varying amounts of Program Mem-
ory. Refer to the device-specific Product Specification for your product to determine the
amount of Program Memory available. Attempts to read or execute from unavailable Pro-
gram Memory addresses return
FFH
. Attempts to write to unavailable Program Memory
addresses produce no effect.
DATA MEMORY
In addition to the Register File and the Program Memory, the eZ8 CPU also accesses a
maximum of 64KB (65,536 bytes) of Data Memory. The Data Memory space provides
data storage only. Opcode and operand fetches cannot be executed out of this space.
Access is obtained by the use of the LDE and LDEI instructions. Valid addresses for the
Data Memory are from
0000H
to
FFFFH
.
Individual products containing the eZ8 CPU support varying amounts of Data Memory.
Refer to the device-specific Product Specification for your product to determine the
amount of Data Memory available. Attempts to read unavailable Data Memory addresses
returns
FFH
. Attempts to write to unavailable Data Memory addresses produce no effect.
STACKS
Stack operations occur in the general-purpose registers of the Register File. The Register
Pair
FFEH
and
FFFH
form the 16-bit Stack Pointer (SP) used for all stack operations. The
Stack Pointer holds the current stack address. The Stack Pointer must be always be set to
point to a section of the Register File that does not cause user program data to be over-
written. Even for linear program code that may not employ the stack for Call and/or Inter-
Table 7. Program Memory Map Example
Program Memory
Address (Hex)
Description
0000-0001
Option Bits
0002-0003
RESET Vector
0004-0005
Watch-Dog Timer Vector
0006-0007
Illegal Instruction Trap Vector
0008-0027
Interrupt Vectors
0028-FFFF
Program code and data
