Technologic Systems TS-3200, User Manual, Page: 27 / 28

TS-3200 User’s Manual Technologic Systems
05/21/2009 27
In the default configuration, P1.5, P1.0 and P3.6 are all initialized as inputs, while P3.0, P3.1, and P3.3
are initialized as "peripherals" (IRQ4, IRQ3, and IRQ5)
Warning: When changing these registers, always use read/modify/write procedures so that
other port pins (used by on-board peripherals) are not affected.
For example, let's say you want to use 386EX Port 3.1 (DIO pin 11) as an output rather than IRQ3 (the
default configuration).
1. Read P3CFG (I/O F824h), AND it with 0FDh, write it back to F824h. (changes from peripheral
to I/O pin)
2. Read P3DIR (I/O F874h), AND it with 0FDh, write it back to F874h. (this made it a
complementary output)
3. To set this pin to a "1", Read P3LTC (I/O F872h), OR it with 02h, write it back.
Note: Because the serial ports are internal to the 386EX, COM1 and COM2 can still use IRQ4 and
IRQ3 even when the associated pins P3.1 and P3.0 are configured as DIO pins DIO1.11 and DIO1.12
– the interrupts are simply no longer available on the PC/104 bus.
Appendix F - Using A 12.5 MHz Baud Clock
Each serial port baud rate generator clock can be independently switched between either the standard
1.85 MHz clock or a 12.5 MHz clock (the internal processor clock divided by 2).
Changing the clock to 12.5 MHz allows baud rates higher than 115 kbaud (up to 781 kbaud), as well as
low error, non-standard lower baud rates (such as 24 kbaud).
The baud rate clock is controlled by I/O location 0F836h:
Bit 0 controls COM1.
Bit 1 controls COM2.
Setting a bit to 0 uses the standard 1.85 MHz clock, and setting a bit to 1 uses the 12.5 MHz processor
clock.
NOTE:
You
must not
modify the other bits of this register. You
must
use a read-modify-write
procedure to change these bits. The following example in assembly illustrates this:
MOV DX, 0F836 ; load the I/O address
IN AL, DX ; read the configuration register
OR AL, 00000001b ; switch COM1 to the 12.5 MHz clock
OUT DX, AL ; write the register
Appendix G - Further References
Technologic Systems Web Site
http://www.embeddedx86.com/
Intel 386EX User's Guide
http://developer.intel.com/design/intarch/manuals/272485.htm
Maxim Integrated Products
http://www.maxim-ic.com/
Omen Technologies
http://www.omen.com/
PC/104 Consortium Web Site
http://www.pc104.org/