Specifications
4 - 5
4.2.4 System I/O Map
Table 4-2 provides a detailed listing of the I/O port assignments used on the Little Board/286.
With the exception of the SCSI controller and configuration EEPROM access register, the I/O port
functions and addresses shown in Table 4-2 are all functionally identical with their counterparts in
a "standard AT" system from both a hardware and software perspective.
In many cases, the board's ROM-BIOS functions provide all of the services that you will need to
control and access devices on the board and connected to its I/O interfaces. If direct programming
of the board's peripheral interfaces is necessary, refer to one of the many available references on
programming the IBM PC and PC/AT for details on programming the standard functions.
Table 4-2. Little Board/286 I/O Map
I/O Address
Function
03F8 - 03FFh
03F0 - 03F7H
03D0 – 03DFh
03C0 – 03CFh
03B0 – 03BFh
03A0 – 03Afh
0380 – 038Fh
0378 – 037Fh
0372 – 0373h
0370 – 0371h
0360 – 036Fh
0300 – 031Fh
02F8 – 02FFh
0278 – 027Fh
0200 – 0207h
01F0 – 01F7h
00F0 – 00FFh
00C0 – 00DFh
00A0 – 00BFh
0080 – 009Fh
0070 – 007Fh
0060 – 006Fh
0040 – 005Fh
0020 – 003Fh
Primary serial port
Floppy disk controller ports (37C65B)
3F2 – FDC Digital output register (LDOR)
3F4 – FDC Main status register
3F5 – FDC Data register
3F7 – FDC Control register (LDCR)
CGA display adapter (option)
EGA display adapter (option)
Monochrome display adapter (option)
Reserved for primary bisync port
Reserved for secondary bisync port
Primary parallel printer port
Configuration EEPROM access register
SCSI controller ports (AIC-6250)
Reserved
Reserved for prototype card
Secondary serial port
Secondary parallel printer port
Reserved for game port
Reserved for AT bus hard disk controller
Math coprocessor (80287)
00F1 – Reset
00F0 – Clear busy
DMA controller 2 (8237 equivalent)
Interrupt controller 2 (8359 equivalent)
DMA page registers (74LS612 equivalent)
Real time clock and NMI mask
Keyboard controller (8042 equivalent)
Programmable timer (8254 equivalent)
Interrupt controller 1 (8359 equivalent)
The remainder of this chapter will examine the above functions, with brief emphasis on the
standard functions, and more detailed emphasis on the unique functions.