Dma Queued Commands - Hitachi T7K250 - Deskstar - Hard Drive Specifications

11.5 DMA queued commands

DMA queued commands are
• Read DMA Queued
• Read DMA Queued Ext
• Service
• Write DMA Queued
• Write DMA Queued Ext
1. Command Issue
a. the host writes any required parameters to the Features, Sector Count, Sector Number, Cylinder, and
Device/Head registers.
b. the host writes command code to the Command Register.
c. the device sets BSY.
d. the device clears or sets REL.
e. the device clears BDY.
2. Data Transfer and Command Completion. If the device is ready for data transfer (REL is cleared),
a. the host transfers the data for the command identified by the Tag number using tghe DMA transfer pro-
tocol currently in effect.
b. the device generates an interrupt to the host when all of the data has been transferred.
c. the host may issue another command or wait for service request from the device.
3. Bus release. If the device is not ready for data ttransfer (REL is sent),
a. the device generates an interrupt if release interrupt is enabled.
b. the host may issue another command or wait for service request from the device.
Deskstar T7K250 Hard Disk Drive Specification
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