Table 4.6.4 Translation Between Nrz And 2-7 Codes - Fujitsu M2361A Customer Engineering Manual

Table 4.6.4 Translation Between NRZ and 2-7 Codes
(3) Write operation
NRZ Code words
1 0
010
o
0 1 0
1 1
011
o
0 I 1
000
2-7 Code words
o
100
100 100
o
0 100 100
1 000
o
0 100 0
000 0 1 000
000 100
The Write circuit block diagram is shown in Figure 4.6.28. The servo data
written on the disk are read by the servo head, and the PLO circuit
generates 2 bit cell FCOI signal. The VCOI signal is applied to the VFO
(variable frequency oscillator).
The VFO is synchronized with the VCOI signal and generates four times the
frequency
0
the VCOl; VF02F signal. VF02F signal is applied to the
ENCODER circuit; VFOlF is also sent to the control unit as the Read Write
Clock signal. The control unit must use this Read Write Clock signal in
the case of Write Clock (WTCL) and Write Data (WTDT) generation.
When a write command is issued from the control unit after head selection,
the WTDT and WTCL signals are sent to the disk drive, and the WTDT signal
is clocked by the positive-going edge of WTCL signal.
The clocked WTDT signal is applied to Encoder circuit, WTDT of NRZ code is
converted into Encode Write Data (ENCWD) of 2-7 code, (refer to Table
4.5.2), and circuit is converted into Write Data Pulse (WDTA).
When the Write Gate signal goes true, the WDTA signal is toggled by a
flip-flop and passes throught he Read/Write Bus Switch IC. It is then
applied to the Head IC (HIC) chips as Data X (DX) and Data Y (DY) signals.
The write current is supplied to the selected HIC chip through a Write
Current (WTCR) line.
The block diagram of write operation is shown in Figure. 4.6.28.
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