C508_01 Datasheet, PDF (15/267 Pages) Infineon Technologies AG – 8-Bit CMOS Microcontroller

C508
Introduction
Table 1-1 Pin Definitions and Functions (cont’d)
Symbol
Pin Numbers
I/O¹⁾ Function
P-MQFP-64 P-SDIP-64
P3.0-P3.7 33 - 40
33
34
35
36
37
38
39
40
41 - 48
41
42
43
44
45
46
47
48
I/O Port 3
is an 8-bit quasi-bidirectional port with internal pull-
up transistors. Port 3 pins that have 1’s written to
them are pulled high by the internal pull-up
transistors and in that state can be used as inputs.
As inputs, Port 3 pins being externally pulled low will
source current (I_IL, in the DC characteristics)
because of the internal pull-up transistors. The
output latch corresponding secondary function must
be programmed to a one (1) for that function to
operate (except for TxD and WR).
The secondary functions are assigned to the pins of
Port 3 as follows:
P3.0 / RxD Receiver data input (asynch.) or data
input/output (synch.) of serial interface
P3.1 / TxD Transmitter data output (asynch.) or
clock output (synch.) of 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 / WR WR control output; latches the data
byte from Port 0 into the external data memory
P3.7 / RD RD control output; enables the external
data memory
User’s Manual
1-7
2001-05