Read Dma (C8H/C9H) - IBM DTCA-23240 - Travelstar 3.2 GB Hard Drive Specifications

12.12 Read DMA (C8h/C9h)

C o m m a n d B l o c k O u t p u t R e g i s t e r s
R e g i s t e r
D a t a
F e a t u r e
S e c t o r C o u n t
S e c t o r N u m b e r
C y l i n d e r L o w
C y l i n d e r H i g h
D e v i c e / H e a d
C o m m a n d
E r r o r R e g i s t e r
7 6 5
C R C U N C 0 I D N
V V 0
Figure 72. Read D M A Command (C8h/C9h)
The Read D M A command reads one or more sectors of data from disk media, then transfers the data from
the device to the host.
The sectors are transferred through the Data Register 16 bits at a time.
The host initializes a slave-DMA channel prior to issuing the command. The data transfers are qualified by
D M A R Q and are performed by the slave-DMA channel. The device issues only one interrupt per command
to indicate that data transfer has terminated and status is available.
If an uncorrectable error occurs, the read will be terminated at the failing sector.
Output Parameters To The Device
Sector Count The number of continuous sectors to be transferred. If zero is specified, then 256
sectors will be transferred.
Sector Number The sector number of the first sector to be transferred. ( L = 0 )
In LBA mode, this register specifies LBA address bits 0 - 7 to be transferred. ( L = 1 )
Cylinder High/Low The cylinder number of the first sector to be transferred. ( L = 0 )
In LBA mode, this register specifies LBA address bits 8 - 15 (Low) 16 - 23 (High) to
be transferred. ( L = 1 )
7 6 5 4 3 2 1 0
V V V V V V V V
V V V V V V V V
V V V V V V V V
V V V V V V V V
1 L 1 D H H H H
1 1 0 0 1 0 0 R
4 3 2 1 0
0 A B T T 0 N A M N
V 0 V 0 V
C o m m a n d B l o c k I n p u t R e g i s t e r s
R e g i s t e r 7 6 5 4 3 2 1 0
D a t a
E r r o r . . . S e e B e l o w . . .
S e c t o r C o u n t V V V V V V V V
S e c t o r N u m b e r V V V V V V V V
C y l i n d e r L o w V V V V V V V V
C y l i n d e r H i g h V V V V V V V V
D e v i c e / H e a d
S t a t u s . . . S e e B e l o w . . .
S t a t u s R e g i s t e r
7 6 5 4 3
B S Y R D Y D F D S C D R Q C O R I D X E R R
0 V 0 V
Command Descriptions
H H H H
2 1 0
0 V
115