4-14 Theory of Operation
as support for the expansion audio mixer chip, the ES978, and a new IIS serial port
and stereo D/A converter. A 4-wire expansion analog bus and 2-wire serial control bus
connect the ES1878 and the ES978.
4.2.5.2 ES1878 Features
♦Hot-dock interface to expansion audio mixer (ES978)
♦Plug-and-Play support using internal resource ROM
♦Monophonic full-duplex using two DMA channels
♦Self-timed joystick port ("digital joystick")
♦Support for up to 7 general purpose outputs and 7 general purpose inputs that
can be slaved with corresponding pins of ES978 in expansion unit
♦IIS interface to intemal stereo D/A for external ZV port or MPEG audio
♦Completely general interrupt mapping, including sharing all interrupts
4.2.6 Keyboard Subsystem
The keyboard subsystem, implemented on the Keyboard Assembly and the Main Board
Assemblies Board, consists of the following major sections:
♦Keyboard Assembly
♦Keyboard Scanner
♦Status LED Interface
4.2.7 I/O Subsystem
The I/O subsystem is implemented with an NS87338VJG Super I/O Controller and the
associated peripherals.
4.2.7.1 NS87338VJG Super I/O Controller
The PC87338VJG is a single chip solution for most commonly used I/O peripherals in
ISA, and EISA based computers. It incorporates a Floppy Disk Controller (FDC), two
full featured UARTs, and an IEEE 1284-compatible parallel port Standard PC-AT
address decoding for all the peripherals and a set of configuration registers are also
implemented in this highly integrated member of the Super I/O family. Advanced power
management features, mixed voltage operation and integrated Serial-lnfrared (both
IrDA and Sharp) support makes the PC87338 an ideal choice for low-power and/or
portable personal computer applications.
The PC87338 FDC uses a high performance digital data separator eliminating the need
for any external filter components. It is fully compatible with the PC8477 and
incorporates a superset of DP8473, NEC PD765 and N82077 floppy disk controller