SM8702AM datasheet(11/16 Pages) NPC

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SM8702AM

NIPPON PRECISION CIRCUITS—11

FUNCTIONAL DESCRIPTION

Mode Setting Overview

There are 2 methods that can be used to set the frequency and clock output start/stop operating modes.

Using external inputs (pins 7, 17, 18, 25, 26, 46) or,

Using data read in from an I2C serial interface.

The default state is where the operating state is set by external pin control. Thus, the output frequency can be

set by FS[0:2] (pins 25, 26, 46). Note that the SSCG function is OFF in this case. If the I2C serial data byte 0

bit 3 is set to 1, then the output frequency is determined by data using the I2C interface. Then, the Spread Spec-

trum function (SSCG) can be selected using I2C data. However, if mode settings using I2C data and external

pin control conﬂict or overlap, the mode settings dictated by I2C data have precedence over external pin con-

trol.

During normal operation, pins 17 and 18 can function as SDRAM clock outputs (desktop mode) or they can

function as CPUCLK output stop control and PCICLK output stop control (mobile mode), depending on the

state of MODE (pin 7) when power is ﬁrst applied.

In addition to output frequency settings, other operating mode settings which can be controlled by I2C serial

data include SSCG operation and mode, and output pin grouping enable/disable switching.

Hardware Frequency Selection

When power is applied, the frequency setting is controlled by FS[0:2] when byte 0 bit 3 is set to 0. Note that if

byte 0 bit 3 is set to 1, the frequency is selected by bits 4 to 6 in the same manner as inputs FS0 to FS2.

Mode and Power Management Inputs

The SM8702AM supports 2 operating modes, desktop mode and mobile mode, selected by MODE (pin 7).

If MODE is HIGH when power is ﬁrst applied, desktop mode is selected. In this mode, pins 17 and 18 function

as SDRAM clock outputs, SDRAM11 and SDRAM10, respectively.

If MODE is LOW when power is ﬁrst applied, mobile mode is selected. In this mode, pins 17 and 18 function

as the CPU clock (CPUCLK[0:1]) and PCI clock (PCICLK[0:4]) output stop control signal inputs,

CPU_STOP# and PCI_STOP#, respectively. This function is used mainly to reduce power consumption.

Inputs

Output frequency

FS2

FS1

FS0

CPUCLK

[MHz]

PCICLK

[MHz]

HIGH

100.2

33.4

HIGH

L O W

1 3 3

33.2

HIGH

L O W

HIGH

112.1

37.3

HIGH

L O W

1 0 3

34.3

L O W

HIGH

66.5

33.2

L O W

HIGH

L O W

83.3

41.6

L O W

HIGH

74.9

37.4

L O W

94.7

31.6

MODE

Pin 17

Pin 18

Mode

HIGH

SDRAM11

SDRAM10

Desktop mode

Pins 17 and 18 are outputs.

L O W

CPU_STOP#

PCI_STO P #

Mobile mode

Pins 17 and 18 are inputs.

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