AT83C51RC2-3CSCM View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
AT83C51RC2-3CSCM Datasheet PDF : 83 Pages
| |||
AT80C51RD2/AT83C51Rx2
Expanded RAM
(XRAM)
The T8xc51Rx2 devices provide additional Bytes of Random Access Memory (RAM)
space for increased data parameter handling and high level language usage.
The devices have expanded RAM in external data space; maximum size and location
are described in Table 7.
Table 7. Expanded RAM
XRAM size
Address
Start
End
T83C51RB2/RC2
T80C51RD2
1024
00h
3FFh
The T8xc51Rx2 has internal data memory that is mapped into four separate segments.
The four segments are:
1. The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly
addressable.
2. The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable
only.
3. The Special Function Registers (SFRs) (addresses 80h to FFh) are directly
addressable only.
4. The expanded RAM bytes are indirectly accessed by MOVX instructions, and
with the EXTRAM bit cleared in the AUXR register (see Table 7).
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.
Figure 5. Internal and External Data Memory Address
0FFh or 3FFh
0FFh
0FFh
0FFFFh
XRAM
Upper
128 Bytes
Internal
RAM
indirect accesses
80h
7Fh
Special
Function
Register
Direct Accesses
80h
External
Data
Memory
Lower
128 Bytes
Internal
RAM
Direct or Indirect
Accesses
00FFh up to 03FFh
00
00
0000
15
4113B–8051–03/05
Share Link: 