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Overview of the ST213 drive, its features, and compatibility with ST225.
Procedure for removing and replacing the PC board in the ST225 drive.
Details on unformatted and formatted capacity, per drive, per surface, per track, per sector.
Defines access time and provides nominal values for track-to-track, average, and maximum seek.
Covers rotational speed, latency, recording density, track density, and data transfer rate.
Mean Time Between Failures (MTBF), Mean Time To Repair (MTTR), and service life.
Operating and non-operating temperature, temperature gradient, and humidity.
Initializes the stepper circuit, resets interface lines, and calibrates heads to Track 0.
Loops waiting for Step pulses; monitors power inputs and resets MPU on transients.
Details control and status signals transmitted via the 34-pin PCB edge-connector J1.
Details how data is recovered via MFM READ DATA lines and flux reversal.
Binary decoder selects desired head based on Head Select lines status.
Amplifies read signal and acts as a high-pass filter for data from selected head.
Attenuates high frequency noise outside the normal data signal range.
Shifts data by 90° to position peak data at the zero crossing point.
Defines transitions written on the disc; +MFM WRITE DATA line is active transition.
Initiates write sequence when activated, applying +12V to head center tap.
Receives differential write data, converts to single line for pulse generator.
Recommended on Tracks 300-614; 12nsec for early/late bits.
Selects Read/Write heads in binary code; 2º and 2² are terminated but unused.
Enables writing to disc, inhibits carriage motion if WRITE FAULT is active.
Microprocessor reset occurs on DC-Unsafe condition, prohibiting writes.
Monitors +5V/+12V lines; disables Write Current if voltage drops too low.
Monitors head selection status, disabling Write Current if multiple/no heads selected.
Notifies host of conditions causing incorrect Write operation; inhibits Write Current.
Details conditions that inhibit Write Current when Write Gate is true.
Status signal indicating drive selection by the host system via TTL open collector.
Indicates beginning of track, transitioning from high to low level once per revolution.
Active only when Read/Write heads are positioned at Cylinder Zero.
Uses reference tracks for initialization, drive speed, and track counter setup.
Details the 16-pin shunt for enabling DRIVE SELECT lines and option selection.
Enables host to select/address drive; options for Daisy-Chain or Radial configuration.
Configuration where drives are chained; last drive needs termination pack.
Option enabled by shorting pins 1 & 2 at J7; drives selected by control cable.
Internal latch for WRITE FAULT signal; cleared by DRIVE SELECT or WRITE GATE.
Manufacturing function where stepper motor continuously seeks; ignores interface signals.
General| Type | HDD |
|---|---|
| Capacity | 20 MB |
| RPM | 3600 |
| Average Seek Time | 85 ms |
| Data Transfer Rate | 5 Mbit/s |
| Interface | ST-506 |
| Form Factor | 5.25-inch |
