ACT apricot - Force Interrupt Command

FLOPPY DISK INTERFACE
Force Interrupt Command
The Force Interrupt command is a Type 4 command and
is used to force the FDC to generate an interrupt via the
INTRQ output on detecting a certain condition. The
conditions are defined by setting certain bits within the
command byte as detailed below.
Type 4 Command
07
DO
11 11 I 0 11 I
13
1 121 Il I 10 I
13
12
x x
x
x
x
1
1
x
0
0
, ,
L-1---Interrupt Condition
Flags.
Interrupt Condition Flags
Il 10
Interrupt Condition
x 1
Not Ready to Ready Transition
1 x
Ready to Not Ready Transition
x x
Every Index
Pulse
x x
Immediate
Interrupt
0 0
No Interrupt
More than one condition can be set at any time by the
appropriate combination of Interrupt Condition Flags.
If any of the Force Interrupt commands are issued to the
Command Register when a command is already in
operation, the current command is terminated and the Busy
bit in the Status Register reset. All the other bits in the
Status Register are left unchanged. If the command is issued
when there is no other command currently in operation, the
Status Register is set to monitor the same conditions as a
Type 1
command, as previously described.
The No Interrupt command functions in an identical
manner to the other Force Interrupt commands, as
described
in the paragraph above, but does not produce an
interrupt request on INTRQ.