CS5530A datasheet(11/259 Pages) NSC

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Architecture Overview (Continued)

1.8

CLOCK GENERATION

In a CS5530A/GX-series processor based system, the

CS5530A generates only the video DOT clock (DCLK) for

the CPU and the ISA clock. All other clocks are generated

by an external clock chip.

The ISACLK is created by dividing the PCICLK. For ISA

compatibility, the ISACLK nominally runs at 8.33 MHz or

less. The ISACLK dividers are programmed via F0 Index

50h[2:0].

DCLK is generated from the 14.31818 MHz input

(CLK_14MHZ). A combination of a phase locked loop

(PLL), linear feedback shift register (LFSR) and divisors

are used to generate the desired frequencies for the DCLK.

The divisors and LFSR are configurable through the

F4BAR+Memory Offset 24h. For applications that do not

use the GX-series processor’s graphics subsystem, this is

an available clock for general purpose use.

Figure 1-4 shows a block diagram for clock generation

within the CS5530A.

Figure 1-4. CS5530A Clock Generation

1.9

UNIVERSAL SERIAL BUS

The CS5530A provides two complete, independent USB

ports. Each port has a Data “–” and a Data “+” pin.

The USB controller is a compliant Open Host Controller

Interface (OpenHCI). The OpenHCI specification provides

a register-level description for a host controller, as well as a

common industry hardware/software interface and drivers

(see OpenHCI Specification, Revision 1.0, for description).

DCLK

PLL

÷N

TVCLK

CLK_14MHZ

ISACLK

PCICLK

CS5530A 데이터시트(PDF) 11 Page - National Semiconductor (TI)