T89C51RD2-SLSIM Atmel, T89C51RD2-SLSIM Datasheet - Page 15

• Manufacturer Part Number: T89C51RD2-SLSIM
• Description: IC MICRO CTRL 64K FLASH 44PLCC
• Manufacturer: Atmel
• Series: 89Cr

Specifications of T89C51RD2-SLSIM

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 1.25K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-PLCC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Data Converters: -

Expanded RAM (XRAM)
Figure 4. Internal and External Data Memory Address
4243G–8051–05/03
FF or 3FF
00
XRAM
The T89C51RD2 provide additional Bytes of random access memory (RAM) space for
increased data parameter handling and high level language usage.
T89C51RD2 devices have expanded RAM in external data space; Maximum size and
location are described in Table 6.
Table 6. Description of Expanded RAM
The T89C51RD2 has internal data memory that is mapped into four separate segments.
The four segments are:
•
•
•
•
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.
•
T89C51RD2
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.)
Instructions that use direct addressing access SFR space. For example: MOV
0A0H, # data ,accesses the SFR at location 0A0H (which is P2).
Port
FF
80
00
indirect accesses
direct or indirect
1024
128 bytes
128 bytes
accesses
Internal
Internal
Upper
Lower
Ram
Ram
XRAM size
FF
80
direct accesses
Function
Register
Special
Start
0100 or 0400
00h
FFFF
0000
Address
T89C51RD2
External
Memory
Data
3FFh
End
15