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Hard Disk Controller (HOC)
The MC68HC99 hard disk controller (HOC) provides an economical solution to
the problem of controlling one or more 3.5 or 5.25 inch hard-disk units. In a single
package the HOC contains a host interface, disk interface, rotating data buffers,
and error detection and correction circuitry. The host interface is the proposed
ANSI X3T9.3 small computer system interface (SCSI) which is compatible with
the Shugart Associates system interface (SASI). It supports single or multi-host
SCSI systems and bus disconnection and reconnection. Disk interfaces
supported are: ST506, 412HP, ESDI step mode, and ESDI serial mode. Two on-
chip data buffers provide fast data throughput without the need for sector
interleaving. The error detection and correction circuitry is based on Reed-
Solomon codes and all detection and correction is done without host system
interaction. The HOC also has 12K bytes of mask-programmable ROM which is
available for user developed firmware.
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