AT89C51RC2-RLTIL Atmel, AT89C51RC2-RLTIL Datasheet - Page 23

• Manufacturer Part Number: AT89C51RC2-RLTIL
• Description: 8-bit Microcontrollers - MCU 80C31 w/4k
• Manufacturer: Atmel

Specifications of AT89C51RC2-RLTIL

• Product Category: 8-bit Microcontrollers - MCU
• Core: 8051
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 60 MHz
• Program Memory Size: 32 KB
• Data Ram Size: 1280 B
• On-chip Adc: No
• Operating Supply Voltage: 2.7 V to 5.5 V
• Package / Case: VQFP-44
• Mounting Style: SMD/SMT
• Interface Type: SPI, UART
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 32
• Number Of Timers: 3
• Program Memory Type: Flash
• Supply Voltage - Max: 3.6 V
• Supply Voltage - Min: 2.7 V

Expanded RAM
(XRAM)
Figure 8. Internal and External Data Memory Address
4180E–8051–10/06
0FFh or 3FFh
00
XRAM
The AT89C51RB2/RC2 provides additional bytes of random access memory (RAM)
space for increased data parameter handling and high-level language usage.
AT89C51RB2/RC2 devices have expanded RAM in external data space; maximum size
and location are described in Table 18.
Table 18. Expanded RAM
The AT89C51RB2/RC2 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
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.
When an instruction accesses an internal location above address 7Fh, the CPU knows
whether the access is to the upper 128 Bytes of data RAM or to SFR space by the
addressing mode used in the instruction.
•
AT89C51RB2/RC2
Part Number
addressable.
only.
addressable only.
with the EXTRAM bit cleared in the AUXR register (see Table 18).
Instructions that use direct addressing access SFR space. For example:
MOV 0A0H, # data, accesses the SFR at location 0A0h (which is P2).
0FFh
80h
7Fh
00
Indirect Accesses
Direct or Indirect
128 Bytes
128 Bytes
Accesses
Internal
Internal
Upper
Lower
RAM
RAM
XRAM Size
1024
0FFh
80h
Direct Accesses
Function
Register
Special
00FFh up to 03FFh
Start
00h
AT89C51RB2/RC2
0FFFFh
0000
Address
External
Memory
Data
3FFh
End
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