Datasheet

4337K–USB–04/08

AT89C5130A/31A-M

8. Program/Code Memory

The AT89C5130A/31A-M implement 16/ 32 Kbytes of on-chip program/code memory. Figure 8-

1 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 erasure 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

voltage. Thus, the Flash Mem-

ory 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 8-1. Program/Code Memory Organization

Note: If the program executes exclusively from on-chip code memory (not from external memory),

beware of executing code from the upper byte of on-chip memory (3FFFh/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.

8.1 External Code Memory Access

8.1.1 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 8-2 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 8-1 describes the exter-

nal memory interface signals.

0000h

32 Kbytes

7FFFh

Flash

32 Kbytes

External Code

FFFFh

AT89C5131A

8000h

0000h

16 Kbytes

3FFFh

Flash

48 Kbytes

External Code

FFFFh

AT89C5130A

4000h