Specifications

or all of the data during this step. During this step, the status of DRQ

is not specified (indicated by

in the diagram).

6. When the data transfer has completed, the drive clears BSY and

asserts INTRQ.

7. After detecting INTRQ, the host resets the slave-DMA channel.

8. The host reads the Status register. In response to the Status register

being read, the drive negates INTRQ.

The following table shows a DMA Data Transfer command with no error.

Step Process BSY DRQ INTRQ

1 Initialize DMA — — —

2 Setup BSY=0 — —

Issue command BSY=0 — —

4 — BSY=0 — —

5 DMA transfer BSY=1 DRQ=

—

6 — BSY=0 — Assert

Reset DMA BSY=0 — Assert

8 Read status BSY=0 — Negate

5.2.4 Nondata commands

A number of ATA commands do not involve data transfer. These com-

mands include Execute Drive Diagnostics, Initialize Drive Parameters,

NOP, Recalibrate, Seek, Set Features, Set Multiple Mode and all of the

Power Management commands.

To execute nondata commands, the host and drive follow these steps:

1. The host writes any required parameters to the Features, Sector

Count, Sector Number, Cylinder and Drive/Head registers.

2. The host writes the command code to the Command register.

3. The drive sets BSY.

4. When the drive has completed processing, it clears BSY and asserts

INTRQ.

5. After detecting INTRQ, the host reads the Status register. In response

to the Status register being read, the drive negates INTRQ.

ATA Interface Reference Manual, Rev. C 31