AT89S4051 Atmel Corporation, AT89S4051 Datasheet - Page 3

• Manufacturer Part Number: AT89S4051
• Manufacturer: Atmel Corporation

Specifications of AT89S4051

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 24 MHz
• Cpu: 8051-12C
• Max I/o Pins: 15
• Uart: 1
• Sram (kbytes): 0.25
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 2
• Isp: SPI

4. Pin Description
4.1
4.2
4.3
4.4
3390E–MICRO–6/08
VCC
GND
Port 1
Port 3
Supply voltage.
Ground.
Port 1 is an 8-bit bi-directional I/O port. Port pins P1.2 to P1.7 provide internal pull-ups. P1.0 and
P1.1 require external pull-ups. P1.0 and P1.1 also serve as the positive input (AIN0) and the
negative input (AIN1), respectively, of the on-chip precision analog comparator. The Port 1 out-
put buffers can sink 20 mA and can drive LED displays directly. When 1s are written to Port 1
pins, they can be used as inputs. When pins P1.2 to P1.7 are used as inputs and are externally
pulled low, they will source current (I
Port 1 also receives code data during Flash programming and verification.
Port 3 pins P3.0 to P3.5, P3.7 are seven bi-directional I/O pins with internal pull-ups.
P3.6 is hard-wired as an input to the output of the on-chip comparator and is not accessible as a
general-purpose I/O pin. The Port 3 output buffers can sink 20 mA. When 1s are written to Port
3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3
pins that are externally being pulled low will source current (I
Port 3 also serves the functions of various special features of the AT89S2051/S4051 as listed
below:
Port 3 also receives some control signals for Flash programming and verification.
Port Pin
P1.5
P1.6
P1.7
Port Pin
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
Alternate Functions
MOSI (Master data output, slave data input pin for ISP channel)
MISO (Master data input, slave data output pin for ISP channel)
SCK (Master clock output, slave clock input pin for ISP channel)
Alternate Functions
RXD (serial input port)
TXD (serial output port)
INT0 (external interrupt 0)
INT1 (external interrupt 1)
T0 (timer 0 external input)
T1 (timer 1 external input)/ PWM output
IL
) because of the internal pull-ups.
IL
AT89S2051/S4051
) because of the pull-ups.
3