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Packet
6.8.
Packet (A0h)
The PACKET command is used to transfer a device command via a command packet (See section 6.1 for
command packet descriptions). If the native form of the encapsulated command is shorter than the packet size
reported in bits 1 and 0 of word 0 of the IDENTIFY PACKET DEVICE response, the encapsulated command shall
begin at byte 0 of the packet. Packet bytes beyond the end of the encapsulated command are reserved. If the
device supports overlap, the OVL bit is set to one in the Features register and the Release interrupt has been
disabled via the SET FEATURES command, the device may or may not perform a bus release. If the device is
ready for the data transfer, the device may begin the transfer immediately as described in the non-overlapped
protocol. If the data is not ready, the device may perform a bus release and complete the transfer after the
execution of a SERVICE command.
Inputs
Register
Features
Sector Count
Sector Number
Byte count low
(Cylinder Low)
Byte count high
(Cylinder High)
Device/Head
Command
Features register -
DMA bit is set to one to inform the device that the data transfer (not the command packet transfer)
associated with this command is via DMA mode.
Sector Count and Sector Number registers -
These fields are not applicable.
Byte count low and Byte count high registers -
These registers are written by the host with the maximum byte count that is to be transferred in any
single DRQ assertion for PIO transfers. The byte count does not apply to the command PACKET
transfer. If the PACKET command does not transfer data, the byte count is ignored.
If the PACKET command results in a data transfer:
a)
the host shall not set the byte count limit to zero. If the host sets the byte count limit to zero the
device sets the limit to FFFEh;
b)
the value set into the byte count limit maybe even or odd;
c)
the value FFFFh is interpreted by the device as though it were FFFEh.
Device/Head register -
DEV indicates the selected device.
Normal outputs
Awaiting command
When the Sony ATAPI Drive is ready to accept the command packet from the host, the register content shall be as
shown below.
SONY AIT-2 Turbo drive SDX-560V series Ver.1.0
7
6
5
na
na
na
1
na
1
6. ATA Command Specification
4
3
2
na
na
na
na
na
Byte count limit (7-0)
Byte count limit (15-8)
DEV
0
A0h
1
0
na
DMA
LUN (0)
6-19
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