C868_02 Datasheet, PDF (45/244 Pages) Infineon Technologies AG – 8 - Bit CMOS Microcontroller

C868
On-Chip Peripheral Components
4
On-Chip Peripheral Components
This chapter gives detailed information about all on-chip peripherals of the C868 except
for the integrated interrupt controller, which is described separately in chapter 7.
4.1
Ports
The C868 has two kinds of ports. The first kind is push-pull ports instead of the traditional
quasi-bidirectional ports. The ports belonging to this kind is port 1 which is a 5-bit I/O port
and port 3 which is an eight-bit I/O port. When configured as inputs, these ports will be
high impedance with Schmitt trigger feature. Port 3 is alternate for capture/compare
functions whereas, port 1 has alternate functions for some of the pins.
The second kind is dedicated ports which are shared by the interrupts, timer 2 inputs,
capture/compare hall inputs and analog inputs.
4.2
I/O Ports
Port 1 and 3 are push-pull ports. Port 1 and port 3 can function as normal I/O ports which
have associated SFRs at address 90_H and B0_H respectively. These ports also have
alternate functions as listed in Table 4-2.
There are three SFRs dedicated for each of these ports. The first one is the port latch
(P1/P3) and second one is direction control register (P1DIR/P3DIR) which is used to set
the direction for each pin. In P1DIR/P3DIR, if the bit is set to 0 the respective port pin is
an output, and 1 means an input. After reset, by default all the Port 1 and 3 pins are
input. The third one is the alternate function register (P1ALT/P3ALT) which is used to
set the function of each pin. When used as alternate function, the direction of the pins
has to be set accordingly.
When the bit is set an input, any read operation will return the value at the port. When
the bit is set as an output, a read operation will return the latched value if it is part of a
read-modify-write operation, otherwise a read operation will return the value at the port.
Note: While in the idle mode or the power down mode the I/O ports hold the last values.
User’s Manual
4-1
V 0.4, 2002-01