USB97C202 datasheet(9/17 Pages) SMSC

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USB 2.0 ATA/ATAPI Controller

Datasheet

SMSC USB97C202

Page 9

Revision 1.2 (02-04-04)

DATASHEET

USB INTERFACE

USB Bus

Data

USB-

USB+

IO-U

These pins connect to the USB bus data

signals.

USB

Transceiver

Filter

LOOPFLTR

This pin provides the ability to supplement the

internal filtering of the transceiver with an

external network, if required.

USB

Transceiver

Bias

RBIAS

A 9.09 Kohm precision resistor is attached

from ground to this pin to set the transceiver’s

internal bias currents.

Termination

Resistor

RTERM

A precision 1.5Kohm precision resistor is

attached to this pin from a 3.3V supply.

Full Speed

USB Data

FS-

FS+

IO-U

These pins connect to the USB- and USB+

pins through 31.6 ohm series resistors.

MEMORY/IO INTERFACE

Memory Data

Bus

MD[7:0]

IO12PU When ROMEN=0, these signals are used to

transfer data between the internal CPU and the

external program memory. When ROMEN=1, a

weak internal pull up is activated to prevent

these pins from floating.

Memory

Address Bus

MA[15:0]

O12

These signals address memory locations within

the external memory.

Memory Write

Strobe

nMWR

O12

Program Memory Write; active low

Memory Read

Strobe

nMRD

O12

Program Memory Read; active low

IO Read

Strobe

nIOR

O12

XDATA space Read; active low

IO Write

Strobe

nIOW

O12

XDATA space Write; active low

MISC

Crystal

Input/External

Clock Input

XTAL1/

CLKIN

ICLKx

12Mhz Crystal or external clock input.

This pin can be connected to one terminal of

the crystal or can be connected to an external

12Mhz clock when a crystal is not used.

Crystal Output XTAL2

OCLKx

12Mhz Crystal

This is the other terminal of the crystal, or left

open when an external clock source is used to

drive XTAL1/CLKIN. It may not be used to

drive any external circuitry other than the

crystal circuit.

Clock Output CLKOUT

This pin produces a 30Mhz clock signal

independent of the processor clock divider. It is

held inactive and low whenever the internal

processor clock is stopped or is being obtained

from the ring oscillator.

Internal ROM

Enable

ROMEN

When left unconnected or tied high, the

USB97C202 uses the internal ROM for

program execution. When tied low, an external

program memory should be connected to the

memory/data bus. The state of this pin latched

internally on the rising edge of nRESET.

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