User guide
56
SmartBook for Renesas R8C/Tiny Microcontrollers
www.MightyMicons.com
Port data registers are the intermediate stage between the
CPU and the port lines managing the external events.
These registers come with input buffers and output latches
for all the available port lines. When the port lines are
already defined as the input lines using port direction
register, reading this port data register gets the levels present
at the corresponding port lines. Similarly when the port lines
are defined as the output lines, corresponding port latches drive
the output status. Proper data should be written in these latches
to control port lines in output configuration. These latches can also
be read to get the status of port lines.
Pull up control registers manage the connection of built-in pull up resistors
with the corresponding port lines. These pull up resistors are connected with the
port lines for a one level defined in this control register. Normally, four port lines
can be tied up with these pull up resistors using a single bit in the control register.
These pull up resistors are connected to the port lines only when these port lines
are used as input lines.
Port drive capacity control registers manage port output drive capacity of the
selected port lines by setting internal output transistors. Each port line has a
controlling bit in this register. By writing one level at these bits, the corresponding
transistors are set to provide high drive capacity at these port lines.
6.3 Analog Interface:
R8C/Tiny controllers come with data converters to monitor the external analog
input voltages as well as to generate external output analog voltages. Normally,
plenty of analog to digital converting circuits are made available to manage a
variety of applications. These A/D circuits contain 10 bit successive approximation
A/D converter with capacitive coupling amplifiers. The analog inputs share the
pins with the port lines. So, these port lines are to be initialized as the input lines
when using corresponding analog inputs. The characteristics of this A/D converter
is given here:
Type of data conversion : Successive approximation.
Resolution : Either 8 bits or 10 bits (selectable).
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Pull up control reg-
isters manage the
connection of built-
in pull up resistors
with the corre-
sponding port
lines.
Port drive capacity con-
trol registers manage port out-
put drive capacity of the se-
lected port lines by set-
ting internal output
transistors.