AT89C5131-PLTIL ATMEL Corporation, AT89C5131-PLTIL Datasheet - Page 46

• Manufacturer Part Number: AT89C5131-PLTIL
• Description: 8-bit Flash Microcontroller with Full Speed USB Device
• Manufacturer: ATMEL Corporation

On-chip Expanded
RAM (ERAM)
Figure 22. Internal and External Data Memory Address
46
AT89C5131
0FFh or 3FFh
00
ERAM
The AT89C5131 provides additional Bytes of random access memory (RAM) space for
increased data parameter handling and high level language usage.
AT89C5131 devices have expanded RAM in external data space; maximum size and
location are described in Table 45.
Table 45. Description of Expanded RAM
The AT89C5131 has on-chip data memory that is mapped into the following four sepa-
rate segments.
1. The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly
2. The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable
3. The Special Function Registers, SFRs, (addresses 80h to FFh) are directly
4. The expanded RAM bytes are indirectly accessed by MOVX instructions, and
The lower 128 bytes can be accessed by either direct or indirect addressing. The Upper
128 bytes can be accessed by indirect addressing only. The Upper 128 bytes occupy
the same address space as the SFR. That means they have the same address, but are
physically separate from SFR space.
Part Number
AT89C5131
addressable.
only.
addressable only.
with the EXTRAM bit cleared in the AUXR register (see Table 45)
0FFh
80h
7Fh
00
indirect accesses
direct or indirect
128 bytes
128 bytes
accesses
Internal
Internal
Upper
Lower
RAM
RAM
ERAM Size
1024
0FFh
80h
direct accesses
Function
Register
Special
00FFh up to 03FFh
Start
00h
0FFFFh
0000
Address
External
Memory
Data
3FFh
End
4136B–USB–09/03