JK microsystems 89-0040, User Manual

JK

microsystems

µFlashTCP-EP 

User’s Manual

6

386Ex Port 3

 bits 0-5, I/O Address F870 and F872 hex

Port 3 bits 0,1,2 and 5 are available on J6, bits 3 and 4 are available on J5.  The data on Port 3
can be read from I/O address F870 hex.  The pins default to inputs.  Each bit of Port 3 can be
individually configured as an input or output. To configure a bit as an output, write a zero to that
bit position in I/O address F874 hex.  To output data on Port 3, write the data to I/O address F872
hex.  When used as inputs, these pins can also be configured to generate processor interrupts.

P3PIN:

F870h, Port Pin Status Register (read only), bits 0-5

P3LTC:

F872h, Port Latch Register, bits 0-5

P3DIR:

F874h, Port Direction Register, bits 0-5, 0 for output, 1 for input or open

drain output.

P3CFG:

F824h, Port Configuration Register, bits 0-5 low, route P3.0-P3.5 to chip
pins (BIOS Default)

Be careful to change only the required bits when working with the I/O ports.  Pins on both ports
are used to control other on-board functions that can be reprogrammed or disabled through these
configuration registers.  See the Intel documentation for more information on configuring these
ports.

REM LED

TheµFlashTCP-EP  is equipped with an LED that can be controlled by user software. This LED is
tied to Port 3 bit 0. Writing a one to this bit will turn the LED on, a zero will turn it off. This port
must be explicitly programmed as an output. See the  section on Port 3 for I/O locations and
programming of this port.

Programming the Ports

The I/O ports are mapped into the 386Ex I/O space. Using the ports requires the use of functions
unique to the x86 family of processors. Creating a pointer to the location may seem logical, but
that reference would be in memory space, not I/O space. Borland C functions 

inport(

port)

and 

outport(

port,value)

 are 16 bit (word) instructions, 

inportb(

port)

 and

outportb(

port,value)

 are 8 bit (byte) instructions. These functions are part of the 

dos.h

header file. Similar functions (and header files) are available for other C compilers and
languages. The following code illustrates the use of 

inportb()

 and 

outportb()

.

unsigned char port;

port = inportb(PORT_DIR);

/* get value of dir. reg */

port |= PORT_DIR_MASK;

/* set dir. bit for input */

outportb(PORT_DIR, port);

/* write value to dir. reg */

printf("PORT: %X\n", (int)inportb(PORT));

/* read & print port value */

Asynchronous Serial (COM) Ports

The µFlashTCP-EP has 2 serial ports, COM1 and COM2.  Both ports are internal to the 386Ex
and are compatible with the UARTs on a PC.  The maximum data rate is 115k Baud.

Hardware