GM82C765B Datasheet, PDF (17/36 Pages) Hynix Semiconductor – FLOPPY DISK SUBSYSTEM CONTROLLER

GM82C765B
* DATA REGISTER
The eight-bit data Register stores data, comma-
nds, parameters, and FDD status information.
Data bytes are read out of, or written into, the
Data Register in order to program or obtain the
results after a particular command.
The relationship between the Master Status
Register and the Data Register Status Register
and the Data Register and the signals
RD , WR , and A0 are shown in Table 7.
TABLE 7. MASTER STATUS AND DATA REGISTERS Relationships
A0
RD
WR
0
0
1
0
1
0
0
0
0
1
0
0
1
0
1
1
1
0
FUNCTION
Read Main Status Register
ILLEGAL
ILLEGAL
ILLEGAL
READ from DATA REGISTER
WRITE into DATA REGISTER
* OPERATIONS REGISTER
The Operations Register provides support logic
that latches the data bus upon receiving
LDOR ad WR . CS should not be active
when this happens. The Operations
Register replaces the typical latched port found
.
in floppy subsystems used to control disk drive
spindle motors and to select the desired disk
drive. Table 8 represents the operations
Register
TABLE 8. OPERATIONS REGISTER
OR0
DSEL
: Drive Select, if low and MOEN1 = 1, then DS1 is active. If high and
MOEN2 = 1, then DS2 is active, but only in the PC AT mode
OR1
(X)
: In GM82C765B this mist be logic 0 for DS1 and DS2 to become active.
No defined function in GM82C765B.
OR2
SRST
: Soft reset, active low.
OR3
DMAEN
: DMA enable, active in Special and PC AT modes, Qualifies DMA and IRQ
outputs and DACK input.
OR4
MOEN1
: Motor On enable, inverted output MO1 is active only in PC AT
OR5
MOEN2
: Motor On enable, inverted output MO2 is active in PC AT
OR6
(X)
: Has no defined function. A spare.
OR7
(MSEL)
: Mode Select, During a soft reset condition, may be used to select
between Special mode (1) and PC AT mode (0).
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