Dma Data Transfer Commands - Hitachi HTS541616J9AT00 - Travelstar 160 GB Hard Drive Specifications

13.4

DMA Data Transfer Commands

These commands are:
•
Read DMA
•
Read DMA EXT
•
Write DMA
•
Write DMA EXT
•
Write DMA FUA EXT
Data transfer using DMA commands differ in two ways from PIO transfers:
•
data transfers are performed using the slave-DMA channel
•
no intermediate sector interrupts are issued on multi-sector commands
Initiation of the DMA transfer commands is identical to the Read Sector or Write Sector commands except that the
host initializes the slave-DMA channel prior to issuing the command.
The interrupt handler for DMA transfers is different in that:
•
no intermediate sector interrupts are issued on multi-sector commands
•
the host resets the DMA channel prior to reading status from the device.
The DMA protocol allows high performance multi-tasking operating systems to eliminate processor overhead
associated with PIO transfers.
1. Host initializes the slave-DMA channel
2. Host writes any required parameters to the Features, Sector Count, LBA High, LBA Mid, LBA Low and
Device registers.
3. Host writes command code to the Command Register
4. The device sets DMARQ when it is ready to transfer any part of the data.
5. Host transfers the data using the DMA transfer protocol currently in effect.
6. When all of the data has been transferred, the device generates an interrupt to the host.
7. Host resets the slave-DMA channel
8. Host reads the Status Register and, optionally, the Error Register
Refer Functional Specification part for further details.
Travelstar 5K160 (PATA) Hard Disk Drive Specification
89 / 188