AT89C51RB2-SLSIM Atmel, AT89C51RB2-SLSIM Datasheet - Page 23

• Manufacturer Part Number: AT89C51RB2-SLSIM
• Description: IC 8051 MCU FLASH 16K 44PLCC
• Manufacturer: Atmel
• Series: 89Cr

Specifications of AT89C51RB2-SLSIM

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 60MHz
• Connectivity: SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-PLCC
• For Use With: AT89STK-11 - KIT STARTER FOR AT89C51RX2
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

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
23