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IN
OUT
IN
OUT
IN
OUT
IN
OUT
C9H -
CAH -
CAH -
CBH -
CBH -
CCH -
CCH -
CDH
&
CDH -
NOT USED
NOT USED
Drive select port.
Data bits 0 and 1 binary weighted select one
of four disk drives.
All subsequent status and comrr.ands will
pertain to the selected drive.
These bits are latched on the
board.
NOT USED
Precisely the same significance as OUT 8AH described above.
Board status port.
This port provides status inforrI)ation on
the drive select, 765 interrupt and drive select delay function
as
follows:
DATA BIT 0 -
A logical one indicates tht a 765 interrupt has
occurred.
DATA BIT 1
a:
2 -
Binary weighted to provide the information on
the drive I, 2, or 3 1S selected.
DATA
BITS
3-6 -
NOT USED
DA TAB IT
7 - A logical one indicates that the floppy disk drive
motors are on and the motor -control time-out is complete.
If the
motor s are off or the time-out is not complete, this bit will be
zero.
Reading this port will start the IPotors and reset tht thirty
(30) second motor-off time-out to zero.
After approximately one
second
thi~
delay conlplete bi t will be set to a logical one.
Board interrupt mask.
The data bits will provide information as
follows:
DATA BIT 0 -
A
one in this pOSitl0n will enable a 765 1nterrupt on
the selected vect ored interrupt line.
A zero disables the interrupt.
DATA BIT 1 -
A one in this positlOn enables a delay complete
interrupt on the selected vectored interrupt line.
Both bit 0 and
1
are latc1">ed on the board.
DATA BITS 2-7 -
NOT USED
Precisely the same significance as IN 8CH and OUT 8CH as described
above.
v
IN
CEH
-
Read main status register of 765 floppy disk controller.
bit 0
=
1
Drive 0 is busy doing seek operation
bit
1
=
1
Drive 1 is busy doing seek oper ation
bit 2
=
1
Drive 2 is busy doing seek operation
. /
bit 3
=
1
Drive 3 is busy doing seek operation
IMS International
5000 Series Microcomputers/7.01.83/page 72
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