Sharp MZ-3500 - Manual (Page 54)

MZ350C
P.n No Signal name I/O Function
32. 31 PSO. 1
Signal used to either advance or delay the write data in writing under the MFM mode,
to obtain timing adjustment for reading. The WDATA signal is controlled as shown in
the table below
PSO PSl FM MFM
0 0 Not changedNot changed
0 1 -
LATE
225~250ns
1 0 -
EARLY
225~250ns
1 1 - -
23 RDATA Read data from the drive unit consists of clock bits and data bits.
22 WINDOW Signal created in the VFO circuit which is used to sample RDATA. Phase syncroniz
carried out in the FDC for RDATA data bits and WINDOW.
5-5. Data recording method
There are two ways of recording data; FM recording
method and MFM recording method.
1) MF recording method
(1) Clock bit indicates a bit cell.
(2) Data bit is placed in a middle of a bit cell. (See Fig. i.)
2) MFM recording method
(1) Data bit IS placed in a middle of a bit cell.
(2) When the data bit is "0", a clock bit is placed before
the current bit cell. (See Fig. 1)
lULJUlJLJLJLJLJlJLn
[ 1
1 1
1 1
i n i
. 1
i
n
1
r
1
1
1
1 r r
1 1
1 1
1 1
1 i
1
1
1
1
1
■
1
0
> i 0
0 0 0 1
(FM recording method)
• (MFM recording method)
As seen from the above illustration, bit density of the MFM
recording method is twice the FM recording method. In
other words, data density of the MFM recording method
doubles that of the FM recording method. For the
Model 3500, only side 0 of track 0 (128 bytes/sector) is
written in the FM mode and rest of other tracks are
recorded in the MFM mode.
5-6. I/O port in the MFD interface
I/O port used in the MFD interface is as follows.
U-BUS I/O
IOMF#F9-AO OUT DACK
D7 ME
D6 SCTRL
D5 TC
D4
OUT
TRIG
D3 SEL3
IOMF#F8-AO 1)2 SEE 2
1)1 SELl
DO SELO
D2 M . ON
D1 IN I NDEX
DO DRQ
Used for data transfer between the CPU and the FDC.
INT from the FDC is output enabled on INTFD.
FDD select signal output is enabled.
TC to FDC.
Trigger (motor on) of the timer (555)
Selects FDD 3
Selects FDD 2
Selects FDD 1
Selects FDD 0
ON/OFF state of the motor
INDEX signal from the motor
DRO from the FDC.
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