UM10147_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 28 April 2008
7 of 134
NXP Semiconductors
UM10147
P89LPC952/954 User manual
P1.2/T0/SCL
2
8
2
I/O
P1.2 —
Port 1 bit 2 (open-drain when used as output).
I/O
T0 —
Timer/counter 0 external count input or overflow output
(open-drain when used as output).
I/O
SCL —
I
2
C-bus serial clock input/output.
P1.3/INT0/SDA 1
7
1
I/O
P1.3 —
Port 1 bit 3 (open-drain when used as output).
I
INT0 —
External interrupt 0 input.
I/O
SDA —
I
2
C-bus serial data input/output.
P1.4/INT1
48
6
44
I/O
P1.4 —
Port 1 bit 4.
I
INT1 —
External interrupt 1 input.
P1.5/RST
47
5
43
I
P1.5 —
Port 1 bit 5 (input only).
I
RST —
External Reset input during power-on or maybe a
reset input/output if selected via UCFG1 and UCFG2. When
functioning as a reset input or input/output, a LOW on this
pin resets the microcontroller, causing I/O ports and
peripherals to take on their default states, and the processor
begins execution at address 0. When functioning as a reset
output or input/output an internal reset source will drive this
pin LOW. Also used during a power-on sequence to force
ISP mode.
When using an oscillator frequency above
12 MHz, the reset input function of P1.5 must be
enabled. An external circuit is required to hold the
device in reset at power-up until V
DD
has reached its
specified level. When system power is removed V
DD
will
fall below the minimum specified operating voltage.
When using an oscillator frequency above 12 MHz, in
some applications, an external brownout detect circuit
may be required to hold the device in reset when V
DD
falls below the minimum specified operating voltage.
P1.6
46
4
42
I/O
P1.6 —
Port 1 bit 6.
P1.7/AD04
43
2
40
I/O
P1.7 —
Port 1 bit 7.
I
AD04 —
ADC0 channel 4 analog input.
P2.0 to P2.5
I/O
Port 2:
Port 2 is an 8-bit I/O port with a user-configurable
output type. During reset Port 2 latches are configured in the
input only mode with the internal pull-up disabled. The
operation of Port 2 pins as inputs and outputs depends upon
the port configuration selected. Each port pin is configured
independently. Refer to
Section 5.1 “Port configurations”
.
All pins have Schmitt triggered inputs.
Port 2 also provides various special functions as described
below:
P2.0/AD07
42
1
39
I/O
P2.0 —
Port 2 bit 0.
I
AD07 —
ADC0 channel 7 analog input.
P2.1/AD06
41
44
38
I/O
P2.1 —
Port 2 bit 1.
I
AD06 —
ADC0 channel 6 analog input.
Table 1.
Pin description
…continued
Symbol
Pin
Type Description
LQFP48
PLCC44
LQFP44