Sharp MZ-350C Service Manual page 54

MZ350C
Pm No.
32. 31
23
22
Signal name
PSO.
1
RDATA
WINDOW
I/O
O
l
l
Function
Signal used
to obtain tir
the table be
to either advance or delay the write data in writ
ning adjustment for readiog. The WDATA signa
ow.
PSO
0
0
1
1
PS1
0
1
0
1
FM
Not changed
-
-
-
MFM
Not changed
LATE
225~250ns
EARLY
225~250ns
-
ng under the MFM mode,
is controlled äs shown in
Read data from the drive unit consists of Clock bits and data bits.
Signal created in the VFO Circuit which is used to sample RDATA. Phase syncroniZ3
:
:: :
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.
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)
JUULJUULJLJl
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. 1.
n
!
0
n
•
1 1 !
i 1 !
0 | 0 i 0 i 0
n
!
(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 M FD Interface
I/O port used in the MFD interface is äs follows.
10MF#F9-AO
IOMF#F8-AO
D- BUS
D7
D6
D5
D4
D3
1)2
Dl
DO
D2
Dl
DO
I/O
OUT
OUT
IN
DACK
ME
SCTRL
TC
TR IG
SEL3
S EI. 2
SEL1
SEI.O
M .ON
I NDEX
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.
TCto FDC.
Trigger (motor on) of the timer (555)
Selects FDD 3
Selects FDD 2
Selects FDD 1
Selects FDDO
ON/OFF state of the motor
INDEX signal from the motor
DRO from the FDC.
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