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1. NONIBM FORMATS
Variatlons in the IBM formats are possibIs to a limited
extent If the followlng requlremsnts are met:
1) Sector slze must be 128,256,512 or 1024 bytes.
2) Gap 2 cannot be varied from the IBM formal.
3) 3 bytes ot A1 must be used in MFM.
In addition, the Index Address Mark Is not required for
Operation by the FD179X. Gap 1,3, and 4 lengths can be as
Short as 2 bytes for FO179X Operation, however PLL lock up
Urne, motor speed Variation, write-splice area, etc. will add
more bytes to each gap to achieve proper Operation. It is
recommended that the IBM format be used for highest
System reliabllity.
Gapl
Gap II
•
Gaplir*
Gap IV
FM
16 bytes FF
11 bytes FF
.
6 bytes 00
10 bytes FF
4 bytes 00
16 bytes FF
MFM
32 bytes 4E
22 bytes 4E
12 bytes 00
3 bytes A1
24 bytes 4E
8 bytes 00
3 bytes A1
16 bytes 4E
* Byte counts must be exact
"Byte counts are minimum, except exactly 3 bytes of A1
mustbewritten.
READ ENABLE TtMING
TIM1NG CHARACTERISTICS
T* = 0°C to 70°C, Vdo = + 12V i .6V, Vs-s = 0V, Vcc =+5V ± .25V
READ ENABLE TIMING (See Nole6, Page 21)
SYMBOL
TSET
THLD
TRE
TDRR
TIRR
TDACC
TDOH
CHARACTERISTIC
Setup AODR & CS to RE
Hold ADDR & CS from RE
RE Pulse Width
ORQ Reset from RE
INTRQ Reset from RE
Data Access from RE
Data Hold From RE
MIN.
50
10
400
50
TYP.
400
500
MAX.
500
3000
350
150
UNITS
nsec
nsec
nsec
nsec
nsec
nsec
nsec
CONOITIONS
Cl = 50 pf
See Note 5
Cl = 50 pt
Cl = 50 pf
WRITE ENABLE TIMING (See Note 6, Page 21)
SYMBOL
TSET
THLD
TWE
TDRR
TIRR
TDS
TDH
CHARACTERISTIC
Setup ADDR & CS to WE
Hold ADDR & CS from WE
WE Pulse Width
DRQ Reset from WE
INTRQ Reset from WE
Data Setup to Wl
Data Hold from WE
MIN.
50
10
350
250
70
TYP.
400
500
MAX.
500
3000
UNITS
nsec
nsec
nsec
nsec
nsec
nsec
nsec
CONDITIONS
See Note 5
59
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