28-03-2012, 11:57 AM
USB2005 and USB97C202 Sharing ATA/ATAPI Drive with Another Controller
datasheet.pdf (Size: 154.05 KB / Downloads: 36)
2 Definitions
The terms assert and negate are used to describe signal state. The terms assert, asserted or assertion
indicate that a signal is active, regardless of that state being represented by a high or low voltage level.
Likewise the terms negate, negated or negation indicate that a signal is not active. Signals that are
asserted when the voltage level is low have a “#” suffix.
3 Functional Requirements
The functional requirement for sharing a media device is that the USB2005 is only enabled when the
ATAC does not need access to the IDE bus and that the USB cable is attached to a host. It is assumed
that the ATAC either generates a signal USB2005_Power_Control# to enable power to the USB2005,
or a signal USB_ATTACH to enable the USB2005 to access the IDE bus. The ATAC has complete
control of the USB2005 via USB2005_Power_Control# or USB_ATTACH and can force the USB2005
off the IDE Bus.
Self-Powered Examples
In a self-powered design an external power source powers the USB2005, ATAC and ATA/ATAPI
device. Figure 4.1 shows an example of a self-powered design. The power source can be either an
external supply or a battery. The ATAC controls when the USB2005 has access to the IDE bus by
driving a FET switch Q1. The USB2005 has access to the ATA/ATAPI drive only when the following
three conditions are true:
n USB cable plugged in to a host, detected when VBUS_DET is asserted
n The ATAC tri-states its IDE bus pins
n The ATAC asserts USB2005_Power_Control#
Summary
The USB2005 can share an IDE bus with another ATA/ATAPI controller. There are many different
applications where this is desired. A few general examples have been discussed in this application
note.