st62t62b STMicroelectronics, st62t62b Datasheet - Page 31

• Manufacturer Part Number: st62t62b
• Description: 8-bit Otp/eprom Mcus With A/d Converter, Auto-reload Timer And Eeprom
• Manufacturer: STMicroelectronics

4 ON-CHIP PERIPHERALS
4.1 I/O PORTS
The MCU features Input/Output lines which may
be individually programmed as any of the follow-
ing input or output configurations:
– Input without pull-up or interrupt
– Input with pull-up and interrupt
– Input with pull-up, but without interrupt
– Analog input
– Push-pull output
– Open drain output
The lines are organised as bytewise Ports.
Each port is associated with 3 registers in Data
space. Each bit of these registers is associated
with a particular line (for instance, bits 0 of Port A
Data, Direction and Option registers are associat-
ed with the PA0 line of Port A).
The DATA registers (DRx), are used to read the
voltage level values of the lines which have been
configured as inputs, or to write the logic value of
the signal to be output on the lines configured as
outputs. The port data registers can be read to get
the effective logic levels of the pins, but they can
Figure 18. I/O Port Block Diagram
S
IN
REGISTER
CONTROLS
SHIFT
S
OUT
TO INTERRUPT
TO ADC
RESET
DIRECTION
REGISTER
REGISTER
REGISTER
OPTION
DATA
DATA
be also written by user software, in conjunction
with the related option registers, to select the dif-
ferent input mode options.
Single-bit operations on I/O registers are possible
but care is necessary because reading in input
mode is done from I/O pins while writing will direct-
ly affect the Port data register causing an unde-
sired change of the input configuration.
The Data Direction registers (DDRx) allow the
data direction (input or output) of each pin to be
set.
The Option registers (ORx) are used to select the
different port options available both in input and in
output mode.
All I/O registers can be read or written to just as
any other RAM location in Data space, so no extra
RAM cells are needed for port data storage and
manipulation. During MCU initialization, all I/O
registers are cleared and the input mode with pull-
ups and no interrupt generation is selected for all
the pins, thus avoiding pin conflicts.
V
ST62T52B ST62T62B/E62B
DD
V
DD
INPUT/OUTPUT
VA00413
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