AT89LP6440 datasheet(10/194 Pages) ATMEL

10 / 194 page

3706A–MICRO–9/09

AT89LP6440 - Preliminary

Memory Organization

The AT89LP6440 uses a Harvard Architecture with separate address spaces for program and

data memory. The program memory has a regular linear address space with support for 64K

bytes of directly addressable application code. The data memory has 256 bytes of internal RAM

and 128 bytes of Special Function Register I/O space. The AT89LP6440 supports external data

memory with portions of the external data memory space implemented on chip as Extra RAM

and nonvolatile Flash data memory. External program memory is not supported. The memory

address spaces of the AT89LP6440 are listed in Table 3-1.

3.1

Program Memory

The AT89LP6440 contains 64K bytes of on-chip In-System Programmable Flash memory for

program storage. The Flash memory has an endurance of at least 100,000 write/erase cycles

and a minimum data retention time of 10 years. The reset and interrupt vectors are located

within the first 83 bytes of program memory (refer to Table 9-1 on page 40). Constant tables can

be allocated within the entire 64K program memory address space for access by the MOVC

instruction. The AT89LP6440 does not support external program memory. A map of the

AT89LP6440 program memory is shown in Figure 3-1.

3.1.1

SIG

In addition to the 64K code space, the AT89LP6440 also supports a 256-byte User Signature

Array and a 128-byte Atmel Signature Array that are accessible by the CPU. The Atmel Signa-

ture Array is initialized with the Device ID in the factory. The second page of the User Signature

Array (0180H–01FFH) is initialized with analog configuration data including the Internal RC

Oscillator calibration byte. The User Signature Array is available for user identification codes or

constant parameter data. Data stored in the signature array is not secure. Security bits will dis-

able writes to the array; however, reads by an external device programmer are always allowed.

In order to read from the signature arrays, the SIGEN bit (DPCF.3) must be set (See Table 5-5

on page 27). While SIGEN is one, MOVC A,@A+DPTR will access the signature arrays. The

User Signature Array is mapped from addresses 0100h to 01FFh and the Atmel Signature Array

is mapped from addresses 0000h to 007Fh. SIGEN must be cleared before using MOVC to

access the code memory. The User Signature Array may also be modified by the In-Application

Programming interface. When IAP = 1 and SIGEN = 1, MOVX @DPTR instructions will access

the array (See Section 3.5 on page 20).

Table 3-1.

AT89LP6440 Memory Address Spaces

Name

Description

Range

DATA

Directly addressable internal RAM

00H–7FH

IDATA

Indirectly addressable internal RAM and stack space

00H–FFH

SFR

Directly addressable I/O register space

80H–FFH

EDATA

On-chip Extra RAM and extended stack space

0000H–0FFFH

FDATA

On-chip nonvolatile Flash data memory

1000H–2FFFH

XDATA

External data memory

3000H–FFFFH

CODE

On-chip nonvolatile Flash program memory

0000H–FFFFH

SIG

On-chip nonvolatile Flash signature array

0000H–01FFH

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