Figure 4.6.27 2-7 Coding - Fujitsu M2361A Customer Engineering Manual

(2) 2-7 coding
Read Current
........ __ - - Disk Rotation
Flu)( reversal (data bit)
Figue 4.6.26 Data Read
Pulse
h - - -
(flux reversal
~--ingap)
~---
Disk Rotation
The M2361A uses the 2-7 recoridng method. Since data is transferred
between the controller and the disk drive unit by NRZ transmission, the
NRZ data is converted to 2-7 data by an encoder in the drive, then
recorded on the magnetic disk. In read operation, the recorded data in
2-7 code is read and converted to NRZ data by a decoder, then transferred
to the controller.
The 2-7 code is a code of 4 to 8 bits in length converted from NRZ data of
2 to 8 bits in length according to the specified rule shown in Table
4.6.4. The 2-7 code contains continuous Os from 2 to 7 between two Is.
In the 2-7 code, the minimum code bit period is more than l.ST (T
indicates the data bit period) for any input data combination.
DATA
1
1 0 0
0 1 1 1 0 1
NRZ
1.5T
U
J
J
2-7
T
Figure 4.6.27 2-7 coding
B03P-482S-0002A ••• 02
0
4 - 89