80C32E
Pin Description
Mnemonic
Type Name and Function
VSS
I
I
Ground: 0V reference
Power Supply: This is the power supply voltage for normal, idle and
power-down operation
VCC
Port 0: Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that
have 1s written to them float and can be used as high impedance inputs.
Port 0 pins must be polarized to Vcc or Vss in order to prevent any
parasitic current consumption. Port 0 is also the multiplexed low-order
address and data bus during access to external program and data
memory. In this application, it uses strong internal pull-up when emitting
1s.
P0.0-P0.7
I/O
I/O
Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. Port 1
pins that have 1s written to them are pulled high by the internal pull-ups
and can be used as inputs. As inputs, Port 1 pins that are externally
pulled low will source current because of the internal pull-ups.
P1.0-P1.7
P2.0-P2.7
Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2
pins that have 1s written to them are pulled high by the internal pull-ups
and can be used as inputs. As inputs, Port 2 pins that are externally
pulled low will source current because of the internal pull-ups. Port 2
emits the high-order address byte during fetches from external program
memory and during accesses to external data memory that use 16-bit
addresses (MOVX @DPTR).In this application, it uses strong internal
pull-ups emitting 1s. During accesses to external data memory that use
8-bit addresses (MOVX @Ri), port 2 emits the contents of the P2 SFR.
I/O
I/O
Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3
pins that have 1s written to them are pulled high by the internal pull-ups
and can be used as inputs. As inputs, Port 3 pins that are externally
pulled low will source current because of the internal pull-ups. Port 3 also
serves the special features of the 80C51 family, as listed below.
I
O
I
RXD (P3.0): Serial input port
TXD (P3.1): Serial output port
P3.0-P3.7
INT0 (P3.2): External interrupt 0
INT1 (P3.3): External interrupt 1
T0 (P3.4): Timer 0 external input
T1 (P3.5): Timer 1 external input
WR (P3.6): External data memory write strobe
RD (P3.7): External data memory read strobe
I
I
I
O
O
Reset: A high on this pin for two machine cycles while the oscillator is
running, resets the device. An internal diffused resistor to VSS permits a
power-on reset using only an external capacitor to VCC.
RST
I
3
4149M–AERO–06/03
AIMTEC [ AIMTEC ]
