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12.19 Read DMA Ext (25h)
The Read DMA command reads one or more sectors of data from disk media, and 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 DMARQ
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.
Table 119 Read DMA Ext Command (25h)
Command Input
Field
Description
FEATURE
Reserved
COUNT
The number of logical sectors to be transferred. A value of 0000h
indicates that 65536 logical sectors are to be transferred
LBA
LBA of first logical sector to be transferred
DEVICE
Bit Description
7 Obsolete
6 Shall be set to one
5 Obsolete
4 Transport Dependent
3:0 Reserved
Command
7:0 25h
Normal Outputs
See Normal Outputs in Section 12.8 Flush Cache Ext (EAh)
Error Outputs
Field
Description
ERROR
Bit Description
7 INTERFACE CRC bit
6 UNCORRECTABLE ERROR bit
5 Obsolete
4 ID NOT FOUND bit
3 Obsolete
2 ABORT bit
1:0 Obsolete
COUNT
Reserved
LBA
LBA of First Unrecoverable Error
DEVICE
Bit Description
7 Obsolete
6 N/A
5 Obsolete
4 Transport Dependent
3:0 Reserved
STATUS
Bit Description
7:6 Transport Dependent
5 DEVICE FAULT bit
4 N/A
3 Transport Dependent
2 N/A
1 SENSE DATA AVAILABLE bit
0 ERROR bit
188
Hard Disk Drive Specification