Rainbow Electronics AT89C51SND1C - Manual (Page 6)

6
AT8xC51SND1C
4109E–8051–06/03
Signals All the AT8xC51SND1C signals are detailed by functionality in Table 1 to Table 14.
Table 1. Ports Signal Description
Table 2. Clock Signal Description
Signal
Name Type Description
Alternate
Function
P0.7:0 I/O
Port 0
P0 is an 8-bit open-drain bidirectional I/O port. Port 0 pins that have 1s
written to them float and can be used as high impedance inputs. To
avoid any parasitic current consumption, floating P0 inputs must be
polarized to V
DD
or V
SS
.
AD7:0
P1.7:0 I/O
Port 1
P1 is an 8-bit bidirectional I/O port with internal pull-ups.
KIN3:0
SCL
SDA
P2.7:0 I/O
Port 2
P2 is an 8-bit bidirectional I/O port with internal pull-ups.
A15:8
P3.7:0 I/O
Port 3
P3 is an 8-bit bidirectional I/O port with internal pull-ups.
RXD
TXD
INT0
INT1
T0
T1
WR
RD
P4.7:0 I/O
Port 4
P4 is an 8-bit bidirectional I/O port with internal pull-ups.
MISO
MOSI
SCK
SS
P5.3:0 I/O
Port 5
P5 is a 4-bit bidirectional I/O port with internal pull-ups.
-
Signal
Name Type Description
Alternate
Function
X1 I
Input to the on-chip inverting oscillator amplifier
To use the internal oscillator, a crystal/resonator circuit is connected to
this pin. If an external oscillator is used, its output is connected to this
pin. X1 is the clock source for internal timing.
-
X2 O
Output of the on-chip inverting oscillator amplifier
To use the internal oscillator, a crystal/resonator circuit is connected to
this pin. If an external oscillator is used, leave X2 unconnected.
-
FILT I
PLL Low Pass Filter input
FILT receives the RC network of the PLL low pass filter.
-