AT89C5131 Datasheet, PDF (26/176 Pages) ATMEL Corporation – 8-bit Flash Microcontroller with Full Speed USB Device

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
FFFFh
32 Kbytes
External Code
8000h
7FFFh1
32 Kbytes
Flash
External Code Memory
Access
Memory Interface
0000h
AT89C5131
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.
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
AT89C5131
P2
A15:8
Flash
EPROM
A15:8
ALE
AD7:0 Latch A7:0
P0
A7:0
PSEN
D7:0
OE
26 AT89C5131
4136B–USB–09/03