AT89LP51 datasheet(23/113 Pages) ATMEL

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3709C–MICRO–5/11

AT89LP51/52 - Preliminary

3.4

In-Application Programming (IAP)

The AT89LP51/52 supports In-Application Programming (IAP), allowing the program memory to

be modified during execution. IAP can be used to modify the user application on the fly or to use

program memory for nonvolatile data storage. The same page structure write protocol for

FDATA also applies to IAP (See Section 3.3.2.1 “Write Protocol” on page 16). The CPU is

always placed in idle while modifying the program memory. When the write completes, the CPU

will continue executing with the instruction after the MOVX @DPTR,A instruction that started the

write.

To enable access to the program memory, the IAP bit (MEMCON.7) must be set to one and the

IAP User Fuse must be enabled. The IAP User Fuse can disable all IAP operations. When this

fuse is disabled, the IAP bit will be forced to 0. While IAP is enabled, all MOVX @DPTR instruc-

tions will access the CODE space instead of EDATA/FDATA/XDATA. IAP also allows

reprogramming of the User Signature Array when SIGEN = 1. The IAP access settings are sum-

marized in Table 3-4 and Table 3-5.

Note:

When In-Application programming is not required, it is recommended that the IAP User Fuse be

disabled.

Table 3-4.

IAP Access Settings for AT89LP52

IAP

SIGEN

DMEN

MOVX @DPTR

MOVC @DPTR

XDATA (0000–FFFFH)

CODE (0000–1FFFH)

XCODE (2000–FFFFH)

001

FDATA (0000–00FFH)

XDATA (0100–FFFFH)

CODE (0000–1FFFH)

XCODE (2000–FFFFH)

XDATA (0000–FFFFH)

SIG (0000–01FFH)

011

FDATA (0000–00FFH)

XDATA (0100–FFFFH)

SIG (0000–01FFH)

CODE (0000–1FFFH)

XDATA (2000–FFFFH)

CODE (0000–1FFFH)

XCODE (2000–FFFFH)

SIG (0000–01FFH)

XDATA (2000–FFFFH)

SIG (0000–01FFH)

Table 3-5.

IAP Access Settings for AT89LP51

IAP

SIGEN

DMEN

MOVX @DPTR

MOVC @DPTR

XDATA (0000–FFFFH)

CODE (0000–0FFFH)

XCODE (1000–FFFFH)

001

FDATA (0000–00FFH)

XDATA (0100–FFFFH)

CODE (0000–0FFFH)

XCODE (1000–FFFFH)

XDATA (0000–FFFFH)

SIG (0000–01FFH)

011

FDATA (0000–00FFH)

XDATA (0100–FFFFH)

SIG (0000–01FFH)

CODE (0000–0FFFH)

XDATA (1000–FFFFH)

CODE (0000–0FFFH)

XCODE (1000–FFFFH)

SIG (0000–01FFH)

XDATA (1000–FFFFH)

SIG (0000–01FFH)

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