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Introduction
Embedded processor solutions often have need of large
amounts of data buffering or program storage which must
be accommodated by the host system. DRAMs for caching
and some type of non-volatile memory,
including EPROM, Flash and RAM,
for boot records are viable but costly
options. The introduction of the Hitachi
Microdrive® in 1999 made possible the
usage of hard disk drive technology to
minimize the dependence on silicon-
based solutions. With a small amount
of additional logic and some simple subroutines, hard disk
drives can easily be used for caching, boot records, and in
some system designs, even customer data.
The Hitachi Microdrive is a CompactFlash® + Type II
device available in various capacities up to 6 Gigabytes in
a package the size of a common matchbook. It requires
a relatively small amount of power to operate, and can
be optimized to further enhance its power utilization in
host systems. The size and power consumption of the
Microdrive make it an ideal solution for many embedded
systems. It can be attached to the processor board and
replaced on an as needed basis, or used to both serve as
a memory extension to support host processor functions
and as the data storage receptacle for large amounts of
end-user data.
Need More System Storage?
Embed a Hitachi Microdrive!
Dr. William F. Heybruck
Senior Storage Engineer
bill.heybruck@hitachigst.com
Theory of operation
The Hitachi Microdrive processes data in 512 byte sectors
and can be accessed in one of three different modes:
Memory, I/O or IDE. In IDE Mode, data can be accessed
using either DMA or UDMA (mode 2) protocol at speeds
up to 33MB/sec. Logical Block Addressing (LBA Mode) is
supported to free the programmer from drive confi guration
concerns such as the number of cylinders, heads, and
sectors. This is a departure from the old DOS days, where
sectors were addressed by Cylinder, Head and Sector (or
CHS). Today, Logical Block Addressing maps the drive into
a sequential r