smc256bf Numonyx, smc256bf Datasheet - Page 66

• Manufacturer Part Number: smc256bf
• Description: 32-mbyte, 64-mbyte, 128-mbyte, 256-mbyte, 512-mbyte, 1-gbyte, 2-gbyte And 4-gbyte 3.3/5 V Supply Compactflash? Card
• Manufacturer: Numonyx

CF-ATA command description
10.10
66/90
Read DMA command (C8h)
This command uses multi-word DMA mode to read from 1 to 256 sectors as specified in the
sector count register. If the sector count is set to ‘0’, 256 sectors will be read by issuing a
Read DMA command.
Data transfer begins at the sector specified in the sector number register. When the Read
DMA command is issued, the CompactFlash card asserts BSY, and transfers all or part of
the sector data in the buffer. The card can then set DRQ and clear BSY, although it is not
required.
The card asserts DMARQ when data are available to be transferred. The host then reads
the 512*sector-count bytes of data from the card using DMA protocol. When DMARQ is
asserted, the host asserts -DMACK to notify it is ready to transfer data, and asserts -IORD
once for each 16-bit word to be transferred.
Interrupts are not generated for each sector transfer, but when all sectors have been
transferred or when an error occurred during the operation.
An abort error is returned by the card when a Read DMA command is sent by the host and
the 8-bit transfer mode has been enabled by the Set Features command.
Table 60
Table 60.
Command (7)
Sect Num (3)
Sect Cnt (2)
Cyl High (5)
Cyl Low (4)
Feature (1)
C/D/H (6)
Bit
defines the Read DMA command byte sequence.
Read DMA
7
LBA
6
5
Cylinder High (LBA 23-16)
Sector number (LBA 7-0)
Cylinder Low (LBA 15-8)
Drive
4
Sector count
C8h
X
3
Head (LBA 27-24)
2
1
SMCxxxBF
0