Service manual

Ultraview 1030/1050 Monitors — Service Manual
3-9
Theory
These clocks are used for specific peripherals and are generated at various locations on the
PCBA.
• 20 MHz clock for Ethernet
• 24.6 MHz clock for audio codec
• 16.9 MHz clock for audio codec
• 12 MHz clock for keyboard/mouse controller
• 14.3 MHz clock for the PCI/ISA bridge and SVGA hardware
• 11.354 MHz divided to 1.89 MHz for SDLC
• 8.33 MHz for the PCI/ISA bridge and ISA bus
Hardware Reset
The hardware reset originates from the MAX695 power supervisor IC. The supervisor IC keeps the
860 PORESET input asserted (thus keeping the CPU from running) when the system voltage is
less than 4.65 V. 200 ms after the system voltage exceeds 4.65 V, the supervisor IC releases the
860 PORESET input, allowing the CPU to boot. The 860 generates two reset outputs, HRESET,
and SRESET. HRESET is buffered and is used to reset all PCI devices and most other major
devices on the PCBA, including ISA devices. ISA devices, however, can also be individually reset
under software control by writing to one of the ISA latches.
Figure 3-4: Reset signals
supervisor
IC chip
MPC860
ISA bus
controller
video
controller
bridge
audio
Ethernet
controller
SRST
Vcc
PCI bus reset
HRST
POreset
IRQ0
power up/down reset
(output only)
pfail
pfail
input
IRTS
reset
kbd/mouse
PCI