Specifications

4 - 3
4.2 OVERALL ARCHITECTURE
As mentioned previously, the Little Board/286 is essentially a complete PC/AT compatible
system, including the equivalent of a motherboard and three or four expansion cards, constructed
on a single electronic assembly that has the same dimensions as a AT expansion card.
Figure 4-1 shows a block diagram of the Little Board/286's onboard logic.
The following sections discuss the Little Board/286 onboard subsystems, grouped as standard
AT system functions and unique functions (not found in standard AT systems):
4.2.1 Standard AT System Functions
n AT Motherboard Logic -- this includes the 80286 CPU, system and extended memory
(up to 4 megabytes, total), ROM-BIOS, DMA controllers, interrupt controllers, system
clocks, programmable timers, keyboard interface, speaker port, battery-backed real time
clock and CMOS RAM (with watch-dog timer option), and the 80287/80C287 math
coprocessor socket.
n Floppy Disk Controller -- a complete AT compatible floppy disk controller.
n Serial/Parallel Controller -- two AT compatible serial ports (with an option of
RS232C/RS422/RS485 driver/receivers on the primary port); and an AT-compatible
parallel printer port (with bidirectional data option).
n AT Expansion Bus -- a full AT compatible (PC bus superset) I/O channel interface
allowing the addition of PC and AT compatible expansion cards.
4.2.2 Unique Functions
n Byte-wide Memory Sockets -- two 28-pin byte-wide sockets which are usable as directly
accessible data or program memory, or as DOS solid state disk (SSD) drives (using the
Ampro SSD Support Software option).
n Configuration EEPROM -- a 1024 bit serial electrically reprogrammable EPROM
device which is used to store system configuration (and other) data. This provides
additional setup configuration functions beyond those normally contained in the
nonvolatile CMOS memory within an AT's battery backed clock device.
n Small Computer System Interface (SCSI) Host Adapter -- a full-function ANSI
X3.131 compatible asynchronous/synchronous SCSI bus interface. The board's ROM-
BIOS supports a one or more SCSI direct access devices (asynchronous usage only) as
AT compatible hard disks.