Sharp MZ-3500 MZ350C, Port used in the MFD interface is as follows, MFM recording method

P,n No	Signal name	I/O
32. 31	PSO. 1	O

23RDATA1

22WINDOW

'

MZ350C

Function

Signal used to either advance or delay the write data in writi ng under the MFM mode, to obtain tir rung adjustment for reading. The WDATA signal is controlled as shown in the table be ow

PSO	PS1	FM	MFM
0	0	Not changed	Not changed
0	1	-	LATE
			225~250ns
1	0	-	EARLY
			225~250ns
1	1	-	-

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 syncroni^i 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)

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.

JUULJUULJLJlJLJLnJl' ' • —1
— 1	i	v	i
n	i	r-JLJLJi !			n
	i	!i	i!	1		• (MFM recording method)
	! n
	i	i	i
i	i				1
	0 ,	0 0 0		o

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.

D-BUS I/O

IOMF#F9-AO OUT

D7

D6

D5

D4

OUT

D3

IOMF#F8-AO 1)2

1)1

DO

U2

Dl IN DO

DACK

ME

SCTRL

TC

TRIG SEL3

SKI. 2 SEL1

SELO

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.

TC to FDC.

Trigger (motor on) of the timer (555) Selects FDD 3

Selects FDD 2

Selects FDD 1

Selects F D D O

ON/OFF state of the motor

INDEX signal from the motor

DRO from the FDC.

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