Datasheet

Application Information
13−4
SLLS535E − April 2008TUSB6250
The IOCS16 signal was defined as IOCS16 in ATA-2, ANSI X3.279-1996, and has been obsolete since ATA-3
was released. IOCS16
is an output from the device to indicate whether the device expects an 8-bit or 16-bit
data transfer.
Because most ATA/ATAPI devices support a 16-bit data transfer, there is no need to support the IOCS16
pin
function.
13.4.2.3 PDIAG:CBLID (Passed Diagnostics: Cable Assembly Type Identifier), Pin 34 on the
ATA/ATAPI Connector
For the TUSB6250, the PDIAG:CBLID signal is not implemented in the hardware. However, developers can
support its function by developing their own custom firmware with the PDIAG
:CBLID signal mapped to
port 3 [6]. Connection to the PDIAG
:CBLID pin of the ATA/ATAPI host connector (the TUSB6250 side) should
be wired accordingly. A jumper selectable capacitor of 0.047 µF can be added to the PDIAG
:CBLID pin of the
ATA/ATAPI connector.
For the ATA specification of ATA-4 and older, the PDIAG
:CBLID signal is only defined as PDIAG, which has
the following characteristics:
• PDIAG
is asserted by device 1 to indicate to device 0 that it has completed diagnostics.
• A 10-kΩ pullup resistor is used on the PDIAG
signal by each device.
• The host should not connect to the PDIAG
signal.
For the ATA specification of ATA-5 and beyond, a cable assembly type identifier (CBLID) function is added
in addition to the PDIAG
signal’s original function.
• To ensure correct functionality, better signal integrity is desired for faster ultra-DMA modes. The optional
80-conductor cable assembly is specified for use with the original 40 connectors. Use of this cable
assembly is mandatory for systems operating at ultra-DMA modes greater than 2.
• Hosts that do not support ultra-DMA modes greater than mode 2 must not connect to the PDIAG
:CBLID
pin.
• In a system using a cable, hosts shall determine that an 80-conductor cable is installed in a system before
operating with transfer modes faster than ultra-DMA mode 2. Hosts must detect that CBLID
is connected
to ground to determine the cable type—see Annex B of the ATA/ATAPI-5 specification for a detailed
explanation.
According to the ATA/ATAPI-5 specification, the host may sample CBLID
after a power-up or hardware reset
in order to detect the presence or absence of an 80-conductor cable assembly by performing the following
steps:
1. The host waits until the power-on or hardware reset protocol is complete for all devices on the cable.
2. If device 1 is present, the host should issue an IDENTIFY DEVICE or IDENTIFY PACKET DEVICE
command and use the returned data to determine that device 1 is compliant with ATA-3 or subsequent
standards. Any device compliant with ATA-3 or subsequent standards releases PDIAG
no later than after
the first command following a power-up or hardware reset sequence.
13.4.2.4 DASP (Device Active, Device 1 Present), Pin 39 on the ATA/ATAPI Connector
The DASP is a time-multiplexed signal that indicates that a device is active or that device 1 is present. The
ATA/ATAPI device is required to have a 10-kΩ pullup resistor on the DASP
pin, because the pin has an
open-drain driver.
For the TUSB6250, the DASP
signal is not implemented in the hardware. However, developers can support
its function by developing their own custom firmware with the DASP
signal mapped to port 3[7]. Connection
to the DASP
pin of the ATA/ATAPI host connector (TUSB6250 side) should be wired accordingly. A selectable
jumper can be added to the DASP
pin connector to allow enable/disable usage of the the DASP pin.