AT89C5131A-RDTUL datasheet(27/186 Pages) ATMEL

27 / 186 page

AT89C5131A-L

4338F–USB–08/07

Program/Code

Memory

The AT89C5131A-L implement 32 Kbytes of on-chip program/code memory. Figure 13

shows the split of internal and external program/code memory spaces depending on the

product.

The Flash memory increases EPROM and ROM functionality by in-circuit electrical era-

sure and programming. Thanks to the internal charge pump, the high voltage needed for

programming or erasing Flash cells is generated on-chip using the standard VDD volt-

age. Thus, the Flash Memory can be programmed using only one voltage and allows In-

application Software Programming commonly known as IAP. Hardware programming

mode is also available using specific programming tool.

Figure 13. Program/Code Memory Organization

Note:

If the program executes exclusively from on-chip code memory (not from external mem-

ory), beware of executing code from the upper byte of on-chip memory (7FFFh) and

thereby disrupting I/O Ports 0 and 2 due to external prefetch. Fetching code constant

from this location does not affect Ports 0 and 2.

External Code Memory

Access

Memory Interface

The external memory interface comprises the external bus (Port 0 and Port 2) as well as

the bus control signals (PSEN, and ALE).

Figure 14 shows the structure of the external address bus. P0 carries address A7:0

while P2 carries address A15:8. Data D7:0 is multiplexed with A7:0 on P0. Table 33

describes the external memory interface signals.

Figure 14. External Code Memory Interface Structure

0000h

32 Kbytes

7FFFh

Flash

32 Kbytes

External Code

FFFFh

AT89C5131A-L

8000h

Flash

EPROM

AT89C5131

AD7:0

A15:8

A7:0

A15:8

D7:0

A7:0

ALE

Latch

PSEN

AT89C5131A-RDTUL 数据表(PDF) 27 Page - ATMEL Corporation

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