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SECTION 2 HARDWARE DESCRIPTION

the on-board processor. The user should refer to FD 1791-01

specifications for a detailed description of this part. Access

to the FD 1791-01 Status Port allows reading the disk interface

signals. These are WRITE PROTECT*, READY*, INDEX*, TRACK-ZERO*,

and SEEKCOMPLETE*.

2.10 DISK INTERFACE

Disk Interface is provided by two gold-plated card edges at

the top of the P.C. board. The 50 pin (J-3) card edge is

intended for the 8" disk drives. The mating connector is the

same type as is used to connect the other side of the ribbon

cable to the disk drive (with most drives). All even numbered

contacts (component side) are connected to internal circuitry

thru a double set of plate-thru-holes. By cutting the connecting

links and adding jumpers, the signal assignments for each

contact can be altered. The 34 pin card edge (J-2) is intended

for 5" disk drives. All unassigned contacts provide a plate-

thru-hole for alteration. Additional signals can be assigned to

this connector by jumping from J-3 to J-2. On connectors J-2 and

J-3 all odd-numbered contacts are grounded.

2.11 INTERNAL I/O ADDRESSES

There are seven I/O ports available to the on-board processor.

These internal ports are not accessible from the host system.

They are used for control signals, status information, and data

paths. They are decoded using address bits AO thru A2.

ADDR TYPE DESCRIPTION

Input

Output

Input

Output

I/O

Board Level Status

Board Level Command

Disk Controller Status

Disk Controller Command

Disk Controller Track

Disk Controller Sector

Disk Controller Data

Table 2-3. Internal I/O Ports

Address bits A3 thru A7 have no effect on I/O operations

except when accessing the Board Level Status Port. These upper

address bits individually trigger on-board events when asserted

high during an INPUT operation from this port. A list is

provided in Table 2-4. For a detailed description refer to the

appropriate section.

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 46 47

Double D 1
. ERRATIC DISK OPERATION 4

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