Parallel ports
ST10F276E
12
Parallel ports
12.1
Introduction
The ST10F276E MCU provides up to 111 I/O lines with programmable features. These
capabilities bring very flexible adaptation of this MCU to wide range of applications.
ST10F276E has nine groups of I/O lines gathered as follows:
●
Port 0 is a two time 8-bit port named P0L (Low as less significant byte) and P0H (high
as most significant byte)
●
●
●
●
●
●
Port 1 is a two time 8-bit port named P1L and P1H
Port 2 is a 16-bit port
Port 3 is a 15-bit port (P3.14 line is not implemented)
Port 4 is a 8-bit port
Port 5 is a 16-bit port input only
Port 6, Port 7 and Port 8 are 8-bit ports
These ports may be used as general purpose bidirectional input or output, software
controlled with dedicated registers.
For example, the output drivers of six of the ports (2, 3, 4, 6, 7, 8) can be configured (bit-
wise) for push-pull or open drain operation using ODPx registers.
The input threshold levels are programmable (TTL/CMOS) for all the ports. The logic level of
a pin is clocked into the input latch once per state time, regardless whether the port is
configured for input or output. The threshold is selected with PICON and XPICON registers
control bits.
A write operation to a port pin configured as an input causes the value to be written into the
port output latch, while a read operation returns the latched state of the pin itself. A read-
modify-write operation reads the value of the pin, modifies it, and writes it back to the output
latch.
Writing to a pin configured as an output (DPx.y=‘1’) causes the output latch and the pin to
have the written value, since the output buffer is enabled. Reading this pin returns the value
of the output latch. A read-modify-write operation reads the value of the output latch,
modifies it, and writes it back to the output latch, thus also modifying the level at the pin.
I/O lines support an alternate function which is detailed in the following description of each
port.
12.2
I/O’s special features
12.2.1
Open drain mode
Some of the I/O ports of ST10F276E support the open drain capability. This programmable
feature may be used with an external pull-up resistor, in order to get an AND wired logical
function.
This feature is implemented for ports P2, P3, P4, P6, P7 and P8 (see respective sections),
and is controlled through the respective Open Drain Control Registers ODPx.
90/235
Doc ID 12303 Rev 3
STMICROELECTRONICS [ ST ]
