Rainbow Electronics T89C51CC02 - Manual (Page 5)

Rev.A - May 17, 2001 5
Preliminary
T89C51CC02
P4.0:1 I/O
Port 4:
Is an 2-bit bi-directional I/O port with internal pull-ups. Port 4 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 4 pins that are
being pulled low externally will be a source of current (IIL, on the datasheet) because of the internal pull-
up transistor.
The output latch corresponding to a secondary function RxDC must be programmed to one for that function
to operate. The secondary functions are assigned to the two pins of port 4 as follows:
P4.0 / TxDC:
Transmitter output of CAN controller
P4.1 / RxDC:
Receiver input of CAN controller.
In the T89C51CC02 Port 4 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.
RESET I/O
Reset:
A high level on this pin during two machine cycles while the oscillator is running resets the device. An
internal pull-down resistor to VSS permits power-on reset using only an external capacitor to VCC.
XTAL1 I
XTAL1:
Input of the inverting oscillator amplifier and input of the internal clock generator circuits.
To drive the device from an external clock source, XTAL1 should be driven, while XTAL2 is left
unconnected. To operate above a frequency of 16 MHz, a duty cycle of 50% should be maintained.
XTAL2 O
XTAL2:
Output from the inverting oscillator amplifier.
Pin Name Type Description