Aaeon PCM-4330, Instructions Manual

Page: 48 / 127

48
Loudspeaker
The tone signal for the speaker is generated by Timer 2 (in the SIS-85C471-AT-
Controller). The timer is programmed as a square-wave generator. The generator is
controlled by the System-Control-Registers in Port B. An additional bit of the Sys-
tem-Control-Registers is combined with output of Timer 2 by a logical and.
Theresulting signal controls the internal or external speaker (using the system inter-
face; c.f. Figure 23 on page 54).
Reset Logic
A system reset may be initiated by the power supply, shutdown, keyboard reset or
via I/O port 92h (Bit 0) and the SIS-85C471-AT-Controller.
A20 Logic
The CPU line mask-A20 can be controlled as in AT-systems through the key-board
controller. Additionally, the PS/2
® -compatible port 92h (Bit 1) is available.
Port B and NMI Logic
The status and control port B (061h) consists of the integrated System-Control-
Register and the System-Status-Buffer. Parity checking may be enabled/disabled
via the System-Control-Register. The System-Status-Buffer informs on queued
memory parity errors.
Video Controller
The Western Digital WD90C24 video controller can address various monochrome
or color flat panel displays directly, as well as regular SVGA monitors. A 2-row 10-
pin connector for SVGA displays and a 2-row 40-pin universal LCD-onnector
arelocated on the board.
Floppy Disk Controller
The FDC37C92x-Ultra-I/O-Controller from SMC with a licensed 765B-compatible
SuperCell
TM
is used for floppy disk control. Data is exchanged over DMA channel2,
interrupts are initiated via IRQ6. Up to two floppy disk drives (3
1/2
or 5
1/4
) are sup-
ported.
IDE-/AT-Bus
The FDC37C92x peripheral unit also includes an interface for IDE-/AT-bus hard
disks.
3.2.10
3.2.9
3.2.11
3.2.12
3.2.13
3.2.14
3.2.15