IBM 3274 51C Maintenance Information page 251

F.1.2.3 Environmental Characteristics
IBM diskette drives can be operated or stored in the follow-
ing temperature and humidity ranges, shown in Figure F-6.
Temperature
Relative
Celsius Fahrenheit Humidity
Operate
10° to 40.6° 50° to 105°
8% to 80%
(Powered On)
Store
10° to 51.7° 50° to 125°
8% to 80%
(Powered Off)
Figure F-6. Environmental Characteristics
F.1.2.4 Functional Characteristics
The format of the data on a diskette is changed when the
number of bytes written in a sector is changed. Diskettes
are used with the formats shown in Figure F-7.
• The maximum number of formatted data bytes per
diskette is shown in Figure F-8.
• Data rate: 250,000 bits (31,250 bytes) per second (FM).
• Cylinder-to-cylinder seek time: 5 ms, plus 35 ms for the
head/carriage assembly to stop. (The total seek time is
the number of cylinders the heads moved across multi--
plied by 5 ms, plus 35 ms.)
• Tracks per diskette side: 77 (cylinder 00 is the label
cylinder; cylinders 01 through 74 are for data; cylinders
75 and 76 are reserved as alternative cylinders).
FM MFM
-16
+
128 bytes per sector
-15-- 26-- 256 bytes per sector
I I
- 8 - - 15 - - 512 bytes per sector
--L l--
1024 bytes per sector
tl.-__ . . . . .
t ___
number of sectors/track
Figure F-7. Data Formats
F-6
Diskette 1 Diskette 2 Diskette 20
128 bytes 246,272
1
492,544
2
per sector
256 bytes 284,160 568,320 985,088
3
per sector
512 bytes 303,104 606,208 1,136,640
per sector
1024 bytes 1,212,416
per sector
1
The total number of data bytes that can be stored on the
diskette. The Basic Data Exchange Standards for exchang-
ing information from one system to another using disk-
ette 1 are:
• Use 128 bytes per sector.
• Do not use track 74.
The total number of usable data bytes then becomes
242,944.
2
Basic Data Exchange for a diskette 2.
3
Basic Data Exchange for a diskette 20.
Figure F-8. Maximum Number of Formatted Data Bytes
F.1.3 Safety
F.1.3.1 Personal Safety
The system or device supplies ac and de power. Ac voltages
are present on the drive motor connector and capacitor ter-
minals in the diskette drive when the drive motor is turning.
Motor and solenoid cases become hot after continuous use;
let the parts cool before servicing them.
The DANGER and CAUTION notices throughout this
appendix are personal safety precautions.
F.1.3.2 Machine Safety
Diskette drives can be damaged if they are not operated or
serviced correctly. The Warning notices in this appendix
are machine safety precautions.
Do not use IBM cleaning fluid or other cleaning fluids near
plastic parts.
Never use damaged diskettes in a diskette drive. Diskettes
that are physically damaged (creased or bent) or contami-
nated (by pencil marks, finger marks, or cleaning fluid) can
cause data errors, equipment errors, or head damage.