ISD-200 Datasheet, PDF (13/64 Pages) List of Unclassifed Manufacturers – USB Mass Storage Class Bulk-Only Specification Compliant

ISD-200 ASIC Datasheet
Introduction
The ISD-200 implements a bridge between one USB 1.1 (http://www.usb.org/developers/data/usbspec.zip)
port and one ATA or ATAPI based mass storage device port. This bridge adheres to the Mass Storage
Class Bulk-Only Transport (http://www.usb.org/developers/data/devclass/usbmassbulk_10.pdf) for ATAPI
transactions. Hardware design allows ATAPI command queuing which allows data transfer rates of up to
the USB theoretical maximum of 12 Mb/sec.
The USB port of the ISD-200 is connected to a host computer directly or via the downstream port of a USB
hub. Host software issues commands and data to the ISD-200 and receives status and data from the ISD-
200 using standard USB protocol.
The ATA/ATAPI port of the ISD-200 is connected to a mass storage device. A large 32 Kbyte buffer
maximizes ATA/ATAPI data transfer rates by minimizing losses due to device seek times. The ATA
interface supports ATA PIO modes 0, 1, and 2.
The device initialization process is configurable, enabling the ISD-200 to initialize most ATA/ATAPI
devices without software intervention. The ISD-200 can also be configured to allow software initialization
of the device if initialization requirements are not supported by ISD-200 algorithms.
ISD-200 Configuration
Certain timing parameters and operational modes in the ISD-200 are configurable and are controlled by a
series of bytes, located at the beginning of the descriptor space.
ISD-200 configuration data is not to be confused with the USB Configuration Descriptor.
ISD-200 Configuration Data and USB Descriptor Sources
ISD-200 configuration data and USB descriptor data in the ISD-200 can be retrieved from several sources,
selected by the mode of operation at power up. This provides for maximal flexibility in configuration
possibilities. There are two possible external sources for descriptor data. Table 2 indicates the method of
determining which of all data sources are used.
ISD-200 configuration and USB descriptor data can be supplied from an I²C serial memory device. The
ISD-200 can address 4 Kbytes of serial ROM data, but USB descriptor information must be limited to 512
bytes maximum. The ISD-200 provides support for the 24LC01-16 family EEPROM interface.
Alternatively, configuration and descriptor data can be supplied by an attached mass storage device through
a vendor-specific Identify (FBh) command. The ISD-200 provides internal RAM (320 bytes) to hold the
data.
The ISD-200 also contains an on-board set of ISD-200 configuration and USB descriptors. Retrieval of the
on-board data will occur if no external descriptor data is supplied (See Table 2). These on-board
descriptors may be used during development, prototyping, and manufacturing.
ISD-200 configuration and descriptor sources are selected by the mode of operation detected at power up.
The following table describes how the ISD-200 determines USB Descriptor sources.
Serial ROM
present
No
I_MODE
Input Pin
0
ISD-200 Configuration and USB Descriptor Retrieval
In this mode, the ISD-200 uses a DIE-ID identifier generated at
fabrication to provide a unique 12-character Serial Number descriptor
string. All other Descriptor and Configuration values are taken from the
In-System Design Confidential
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