IBM DTCA-24090 Hard Drive Specifications - Page 123

Read DMA, C8h/C9h

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12.12 Read DMA (C8h/C9h) Command Block Output Registers Register 76543210 Data Feature Sector Count V V V V V V V V Sector Number V V V V V V V V Cylinder Low V V V V V V V V Cylinder High V V V V V V V V Device/Head 1L1DHHHH Command 1100100R Command Block Input Registers Register 76543210 Data Error ...See Below... Sector Count V V V V V V V V Sector Number V V V V V V V V Cylinder Low V V V V V V V V Cylinder High V V V V V V V V Device/Head HHHH Status ...See Below... Error Register 76543210 CRC UNC 0 IDN 0 ABT T0N AMN VV0V0V0V Status Register 76543210 BSY RDY DF DSC DRQ COR IDX ERR 0V0V 0 V Figure 72. 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 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. 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 ) Command Descriptions 115

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12.12
Read DMA
(C8h/C9h)
Command Block Output Registers
Command Block Input Registers
Register
76543210
Register
76543210
Data
Data
Feature
Error
...See Below...
Sector Count
VVVVVVVV
Sector Count
VVVVVVVV
Sector Number
VVVVVVVV
Sector Number
VVVVVVVV
Cylinder Low
VVVVVVVV
Cylinder Low
VVVVVVVV
Cylinder High
VVVVVVVV
Cylinder High
VVVVVVVV
Device/Head
1L1DHHHH
Device/Head
HHHH
Command
1100100R
Status
...See Below...
Error Register
Status Register
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
CRC UNC
0
IDN
0
ABT T0N AMN
BSY RDY DF
DSC DRQ COR IDX ERR
V
V
0
V
0
V
0
V
0
V
0
V
0
V
Figure 72. 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
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.
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)
Command Descriptions
115