Rainbow Electronics T89C51CC02 - Manual (Page 4)

4 Rev.A - May 17, 2001
Preliminary
T89C51CC02
Table 1. Pin Description
Pin Name Type Description
VSS GND Circuit ground potential.
VCC Supply voltage during normal, idle, and power-down operation.
VAREF Reference Voltage for ADC
VAVCC Supply Voltage for ADC
VAGND Reference Ground for ADC / Analog Ground
P1.0:7 I/O
Port 1:
is an 8-bit bi-directional I/O port with internal pull-ups. Port 1 pins can be used for digital input/output
or as analog inputs for the Analog Digital Converter (ADC). Port 1 pins that have 1’s written to them
are pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port
1 pins that are being pulled low externally will be the source of current (IIL, on the datasheet) because
of the internal pull-ups. Port 1 pins are assigned to be used as analog inputs via the ADCF register.
As a secondary digital function, port 1 contains the Timer 2 external trigger and clock input; the PCA
external clock input and the PCA module I/O.
P1.0 / AN0 / T2
Analog input channel 0,
External clock input for Timer/counter2.
P1.1 / AN1 / T2EX
Analog input channel 1,
Trigger input for Timer/counter2.
P1.2 / AN2 / ECI
Analog input channel 2,
PCA external clock input.
PIn the T89C51CC02 Port 1 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
P2.0:1 I/O
Port 2:
Is an 2-bit bi-directional I/O port with internal pull-ups. Port 2 pins that have 1’s written to them are
pulled high by the internal pull-ups and can be used as inputs in this state. As inputs, Port 2 pins that
are being pulled low externally will be a source of current (IIL, on the datasheet) because of the internal
pull-ups.
In the T89C51CC02 Port 2 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
P3.0:7 I/O
Port 3:
Is an 8-bit bi-directional I/O port with internal pull-ups. Port 3 pins that have 1’s written to them are
pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port 3
pins that are being pulled low externally will be a source of current (IIL, on the datasheet) because of the
internal pull-ups.
The output latch corresponding to a secondary function must be programmed to one for that function to
operate. The secondary functions are assigned to the pins of port 3 as follows:
P3.0 / RxD:
Receiver data input (asynchronous) or data input/output (synchronous) of the serial interface
P3.1 / TxD:
Transmitter data output (asynchronous) or clock output (synchronous) of the serial interface
P3.2 / INT0:
External interrupt 0 input / timer 0 gate control input
P3.3 / INT1:
External interrupt 1 input / timer 1 gate control input
P3.4 / T0:
Timer 0 counter input
P3.5 / T1:
Timer 1 counter input
P3.6
P3.7
In the T89C51CC02 Port 3 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.