AT89C5131-RDTIL datasheet(26/176 Pages) ATMEL

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AT89C5131

4136B–USB–09/03

Program/Code

Memory

The AT89C5131 implement 32 Kbytes of on-chip program/code memory. Figure 11

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 V

DD 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 11. 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 12 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 12. External Code Memory Interface Structure

0000h

32 Kbytes

7FFFh1

Flash

32 Kbytes

External Code

FFFFh

AT89C5131

8000h

Flash

EPROM

AT89C5131

AD7:0

A15:8

A7:0

A15:8

D7:0

A7:0

ALE

Latch

PSEN

AT89C5131-RDTIL Datasheet(PDF) 26 Page - ATMEL Corporation

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