ST7LITE20F2 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
ST7LITE20F2
STMicroelectronics
'ST7LITE20F2' PDF : 170 Pages View PDF
ST7LITE20F2 ST7LITE25F2 ST7LITE29F2
I/O ports
10.2.3 Alternate functions
Caution:
Many ST7s I/Os have one or more alternate functions. These may include output signals
from, or input signals to, on-chip peripherals. The Device Pin Description table describes
which peripheral signals can be input/output to which ports.
A signal coming from an on-chip peripheral can be output on an I/O. To do this, enable the
on-chip peripheral as an output (enable bit in the peripheral’s control register). The
peripheral configures the I/O as an output and takes priority over standard I/O programming.
The I/O’s state is readable by addressing the corresponding I/O data register.
Configuring an I/O as floating enables alternate function input. It is not recommended to
configure an I/O as pull-up as this will increase current consumption.
Before using an I/O as an alternate input, configure it without interrupt. Otherwise spurious
interrupts can occur.
Configure an I/O as input floating for an on-chip peripheral signal which can be input and
output.
I/Os which can be configured as both an analog and digital alternate function need special
attention.
The user must control the peripherals so that the signals do not arrive at the same time on
the same pin. If an external clock is used, only the clock alternate function should be
employed on that I/O pin and not the other alternate function.
Figure 31. I/O port general block diagram
Register
access
DR
Alternate
output
1
From on-chip peripheral
0
Alternate
enable
bit
VDD
P-buffer
(see table below)
PULL-UP
(see table below)
VDD
DDR
OR
OR SEL
If implemented
DDR SEL
DR SEL
1
0
External
interrupt
request (eix)
Combinational
Logic
Sensitivity
selection
From
other
bits
.
Pull-up
condition
PAD
N-buffer
CMOS
Schmitt
trigger
Diodes
(see table below)
Analog
input
Alternate
input
To on-chip peripheral
Doc ID 8349 Rev 5
65/166
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