AT89LP51RB2 Atmel Corporation, AT89LP51RB2 Datasheet - Page 15

• Manufacturer Part Number: AT89LP51RB2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RB2

• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 42
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Adc Channels: 7
• Adc Resolution (bits): 10
• Adc Speed (ksps): 153.8
• Sram (kbytes): 1.375
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

3722A–MICRO–10/11
Figure 3-2.
Figure 3-3.
In order for Fast mode to fetch externally, two wait states must be inserted for every clock cycle,
increasing the instruction execution time by a factor of 3. However, due to other optimizations,
external Fast mode instructions may still be 1/4 to 1/2 faster than their Compatibility mode equiv-
alents. Note that if ALE is allowed to toggle in Fast mode, there is a possibility that when the
CPU jumps from internal to external execution a short pulse may occur on ALE as shown in
ure
this behavior can be avoided by setting the DISALE bit prior to any jump above the 8K border.
Figure 3-4.
3-4. The setup time from the address to the falling edge of ALE remains the same. However,
DISALE=0
DISALE=1
PSEN
PSEN
CLK
ALE
CLK
ALE
ALE
P0
P2
P0
P2
Executing from External Program Memory
External Program Memory Fetches
Internal/External Program Memory Boundary (Fast Mode)
DATA
SAMPLED
INTERNAL EXECUTION
PCL
OUT
AT89LP51RB2/RC2/IC2 Preliminary
P0 SFR OUT
P2 SFR OUT
P1
P3
AT89LP
PSEN
PCH OUT
FLOAT
ALE
P0
P2
LATCH
DATA
SAMPLED
PCL OUT
OUT
PCL
SHORT
PULSE
PCH OUT
PCH OUT
FLOAT
EXTERNAL
INSTR.
OE
PROGRAM
EXTERNAL EXECUTION
MEMORY
ADDR
DATA
SAMPLED
DATA
SAMPLED
PCL OUT
OUT
PCL
PCH OUT
PCH OUT
Fig-
15