ISD-200 Datasheet, PDF (29/64 Pages) List of Unclassifed Manufacturers – USB Mass Storage Class Bulk-Only Specification Compliant

ISD-200 ASIC Datasheet
Device Requirements
Attached mass storage devices must support the following device requirements.
ATA Power Supplied from the USB Bus
Power requirements for the device vary depending upon the mode used. If no serial ROM is present and
IMODE is asserted, the device must be capable of operating at 4.4V when in enumeration mode (100 mA).
That is, when obtaining configuration and USB descriptor information from the device using the vendor-
specific Identify (FBh) command. After enumeration, the device must be able to operate at 4.75V when in
operational mode (500 mA).
If a serial ROM is used, the device must be able to operate at 4.75V when obtaining configuration and USB
descriptor information.
ATA Reset, A1h, FBh
BSY and DRQ must be cleared by the device prior to the amount of time specified by ATA Initialization
Timeout configuration field has passed since the removal of reset.
ATA Polling Device
The device shall be capable of being a polling only device. As such, the ATA signal INTRQ is not
required but may be useful as a debug tool.
ISD-200 ATA Bus State During Idle
The ISD-200 drives the address lines high and the last contents of the data register onto the ATA bus when
idle. Pull up or pull down resistors shall not be used in bus power systems as the drive supply power will
be shut off in USB suspend mode.
ATA PIO Support
Register accesses are performed in PIO mode 0 (750 ns cycle time). The maximum data register accesses
are performed in PIO mode 2 (292 ns cycle time). The ISD-200 configuration bytes must be set such that
data register accesses do not exceed the maximum speed supported by the device.
ATA Initialization Timeout
The ISD-200 supports a default configuration of 3.2 seconds for ATA Initialization Timeout. If a serial
ROM is used, its ATA Initialization Timeout configuration value will override the default prior to device
initialization. If no serial ROM is used and I_MODE is asserted, subsequent device initializations will use
the ATA Initialization Timeout configuration value supplied by the vendor-specific Identify (FBh)
command.
Reset Recovery shall be 3 ms. The following figure graphically defines “Initialization Timeout” and
“Reset Recovery”.
ATA_NRESET
reset assertion
initialization
timeout
reset recovery
nDIOR/nDIOW
In-System Design Confidential
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