Figure 11-8. flow diagram—dma command protocol – Freescale Semiconductor MPC5200B User Manual

Page 399

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MPC5200B Users Guide, Rev. 1

11-34

Freescale Semiconductor

ATA Bus Background

Figure 11-8. Flow Diagram—DMA Command Protocol

Host:

BSY = 0 &

DRQ = 0

No

Host:

BSY = 0 &

DRQ = 0

No

Yes

Yes

Drive:

Error

Yes

No

Drive:

Transfer

Done

Drive:

Error

Drive:

nIEN = 0

No

Yes

No

Yes

No

Yes

Write Command Code

to Command register

Write Control/Command block

registers to setup data transfer

Drive: Set BSY = 1 and

begin command execution

Host: Read Status or

Alternate Status register

Host: Write Device/Head

register to select drive

Host: Read Status register

Host: Read Status or

Alternate Status register

Drive: Assert DMARQ when

ready to transfer data

Drive: Negate INTRQ

Host: Read Status register

Drive: Assert INTRQ

Drive: Clear BSY = 0 and DRQ = 0

Drive: Set error status

Host: Assert DMACK when

ready to transfer data

START

END

Drive: Set BSY = 1, or

BSY = 0 & DRQ = 1

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