HP C2233 Product Description Manual page 54

phases involved in each transaction. Full arbitration
and disconnect/reselection are implemented by the SCSI
interface.
RAM Buffer
The RAM Buffer contains 64-kilobytes of static RAM. All
data transferred between the host and the disk must pass
through the RAM buffer.It is protected by an additional 2
bits of parity for each 16-bit word transferred by the DMA.
Disk Controller
The disk controller coordinates the flow of data by
interleaving RAM accesses between the SCSI interface
Data
Encoder/Decoder
and the disk controller. It contains a DMA section which
controls the transfer of data between the SCSI interface,
the buffer RAM and the disk controller. The DMA accesses
the 64-kilobyte) static RAM buffer to match the transfer
speeds of the SCSI interface and the disk controller.
The disk controller also performs error checking on data
being transferred from the disk to the RAM buffer and
generates ECC on data transferred from the RAM buffer to
the disk. The data controller also does header verification
during read/write operations.
The primary function of the Data Encoder/Decoder is to
convert between the NRZ (Non Return to Zero) data/clock
present on the SCSI Channel and RLL (Run Length
Limited, 2-7) data transferred to and from the disk surface.
This includes sector length and content information
provided by the host during format operations as well as
data transfers during normal Read and Write operations.
Microcontroller
The microcontroller used on the drive/electronics PCA
is an 80Cl96 single-chip device operating at 10.3 Mhz.
The microcontroller is responsible for decoding incoming
SCSI commands, controlling the servo processor and the
read/write circuitry, and managing the head alignment
function.
3-14 Product Features DRAFT
10/24/90 11:07