The CY2254A is a Clock Synthesizer/Driver that provides the
multiple clocks required for a Pentium-based PC. The
CY2254A has low-skew outputs (< 250 ps between the CPU
Clocks, < 250 ps between the PCI Clocks). In addition, the
CY2254A CPU clock outputs have less than 200 ps cycle-
to-cycle jitter. Finally, both the PCI and CPU clock outputs
meet the 1 V/ns slew rate requirement of a Pentium processor-
based system.
The CY2254A accepts a 14.318 MHz reference signal as its
input. The CY2254A has 2 PLLs, one of which generates the
CPU and PCI clocks, and the other generates the I/O and Keyboard
Controller or USB clocks. The CY2254A runs off either
a 3.3V or 5V supply.
The CY2254A is available in two options. The ?1 option supports
the Intel Triton PCIset and provides a 12 MHz keyboard
clock on pin 25. The ?2 option provides a 48 MHz USB clock
on pin 25 and supports the Cyrix? M1 processor.