Read Dma (C8H/C9H); Figure 93. Read Dma Command (C8H/C9H) - IBM IC25N020ATDA04 - Travelstar 20 GB Hard Drive Specifications

13.14 Read DMA (C8h/C9h)

Command Block Output Registers
Register
Data
Feature
Sector Count
Sector Number
Cylinder Low
Cylinder High
Device/Head
Command
Error Register
7 6 5
CRC UNC 0
V V 0

Figure 93. Read DMA command (C8h/C9h)

The Read DMA 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
the DMARQ and are performed by the slave-DMA channel. The device issues only one interrupt per
command to indicate that the data transfer has terminated and that status is available.
If an uncorrectable error occurs, the read will be terminated at the failing sector.
Output Parameters To The Device
Sector Count
Sector Number
Cylinder High/Low
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
IDN 0 ABT T0N AMN
V 0 V 0
This indicates the number of continuous sectors to be transferred. If zero is
specified, then 256 sectors will be transferred.
This indicates the sector number of the first sector to be transferred. (L = 0) In
LBA mode, this register specifies that LBA address bits 0–7 are to be transferred.
(L = 1)
This indicates the cylinder number of the first sector to be transferred. (L = 0) In
LBA mode, this register specifies LBA address bits 8–15 (Low) and 16–23 (High)
to be transferred. (L = 1)
Travelstar 48GH, 30GN & 15GN hard disk drive specifications
Command Block Input Registers
Register
Data
Error
Sector Count
Sector Number
Cylinder Low
Cylinder High
Device/Head
Status
Status Register
0 7 6 5
BSY RDY DF
V 0 V 0
139
7 6 5 4 3 2 1 0
- - - - - - - -
see below
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
- - - - H H H H
see below
4 3 2 1 0
DSC DRQ COR IDX ERR
V - 0 - V