AT83C5136-RDTUL datasheet(26/171 Pages) ATMEL

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AT83C5134/35/36

7683B–USB–03/07

Program/Code

Memory

The AT83C5134/35/36 implement 16 or 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.

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 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 32

describes the external memory interface signals.

Figure 14. External Code Memory Interface Structure

0000h

32 Kbytes

7FFFh

ROM

32 Kbytes

External Code

FFFFh

8000h

0000h

16 Kbytes

3FFFh

ROM

48 Kbytes

External Code

FFFFh

4000h

AT83C5135

AT83C5136

Flash

EPROM

AT89C5131

AD7:0

A15:8

A7:0

A15:8

D7:0

A7:0

ALE

Latch

PSEN

AT83C5136-RDTUL データシート(PDF) 26 Page - ATMEL Corporation

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