Service manual

Ultraview 1030/1050 Monitors — Service Manual
3-7
Theory
Audio
The Audio subsystem is based on a Crystal CS 4231A Multimedia Codec. This chip is capable of
supporting simultaneous stereo in and out, however the device is used only in monophonic mode
in a 1030/1050 monitor. An audio amp is used for the internal speaker, and op-amp buffers are
used to drive the line out connector.
For diagnostics, the line out and the speaker signals can be fed back into the line in pins to verify
that the audio outputs are operating correctly. This is controlled by writing to a register in the codec
(this feature has not yet been implemented).
Wireless LAN Card
The wireless LAN is implemented using the Proxim Inc. RangeLAN2/OEM card. This device
mounts on the CPU PCBA and connects to the ISA bus via a flex cable. A chip-select signal is
generated from the ISA addresses by the ISA EPLD and is used to select the wireless LAN card.
An interrupt is also provided from the wireless card to the MPC860 CPU to inform the CPU that the
card has data. All timing is essentially ISA standard. The wireless card resides in ISA I/O space.
All data transfer is performed via software programmed I/O — the wireless LAN card does not
support DMA (direct memory access). All communications to and from the card are in the form of
packets. These packets contain received data or data for transmission or commands to the
wireless LAN card.
Non-Volatile RAM/Real-time Clock
The NVRAM and real-time clock (NVRAM RTC, refer to Figure 3-3) reside on the ISA bus. Both
functions are implemented with a Dallas Semiconductor DS1644 Non-volatile Timekeeping RAM.
The NVRAM chip contains the following functions:
• A 32K × 8 Static RAM.
• A time-of-day clock, which overlays the uppermost 8 RAM addresses.
• An integrated lithium battery with a 10 to 20 year lifetime.
• An integrated clock crystal with ±1 minute/month accuracy.
• Power-fail circuitry to protect the clock and RAM on power down.
The NVRAM is used to hold sysgen values, error logs, and other miscellaneous system data. The
real-time clock keeps track of time while the unit is ON or OFF. An enable bit in the ISA bridge chip
must be set to enable writing to the NVRAM. The device is socket mounted for easy replacement.
Keyboard/Mouse Interface
The keyboard and mouse interface (K/M CTRL, refer to Figure 3-3) is implemented with the Intel
82C42PE programmable interface chip. This device resides on the ISA bus. This device comes
pre-programmed with a Phoenix keyboard/PS-2 mouse BIOS.
ISA I/O Buffers
These latches and buffers interface miscellaneous low-frequency status and control signals to the
ISA bus.