PACKET - A0h, Data

PACKET - A0h, Data

Inputs:

Register	7	6	5	4	3	2		1	0
Features	na	na	na	na	na	na		OVL	DMA
Sector Count	Tag					na
LBA Low	na
Byte Count low (LBA Mid)	Byte Count limit (7:0)
Byte Count high (LBA High)	Byte Count limit (15:8)
Device	obs	na	obs	DEV	na	na	na			na
Command	A0h

Features register -

• OVL - This bit is set to one to inform the device that the PACKET command is to be overlapped.
• DMA - This bit is set to one to inform the device that the data transfer (not the command packet transfer) associated with this command is via Multiword DMA or Ultra DMA mode.

Sector Count register -

• Tag - If the device supports command queuing, this field contains the command Tag for the command being delivered. A Tag may have any value between 0 and 31 regardless of the queue depth supported. If queuing is not supported, this field is 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.

Normal Outputs:

Register

7

6

5

4

3

2

1

0

Error

na

Interrupt reason (Sector Count)

na

REL

I/O

C/D

LBA Low

na

Byte Count low (LBA Mid)

Byte Count (7:0)

Byte Count high (LBA High)

Byte Count (15:8)

Device

obs

na

obs

DEV

na

na

na

na

Status

BSY

na

DMRD

SERV

DRQ

na

na

CHK

Interrupt reason register -

• Tag - If the device supports command queuing and overlap is enabled, this field contains the command Tag for the command. A Tag value may be any value between 0 and 31 regardless of the queue depth supported. If the device does not support command queuing or overlap is disabled, this field is not applicable.
• REL - Shall be cleared to zero.
• I/O - Shall be cleared to zero indicating transfer to the device.
• C/D - Shall be set to one indicating the transfer of a command packet. 

Device register -

• DEV shall indicate the selected device.

Status register -

• BSY - Shall be cleared to zero.
• DMRD (DMA ready) - Shall be cleared to zero.
• SERV (Service) - Shall be set to one if another command is ready to be serviced. If overlap is not supported, this bit is command specific.
• DRQ - Shall be set to one.
• CHK - Shall be cleared to zero.