Floppy Disk Controller; Floppy Disk Control Port - ADC Super Net S-100 Technical Manual

4.7 Floppy Disk Control port
14 Read/Write
Port Read :
FOC syncronization/Drive/Density
When the cpu reads this port the cpu is placed into a wait
state until a data byte can be transfered to or from the floppy
disk controller or untill the command complete/terminate status
(INTRQ) is set by the floppy disk controller. The floppy disk
controller INTRQ status bit is placed on the data bus as bit 07.
This bit can be tested to determine if data is to be transfered
of if the command is complete.
+----+----+----+----+----+----+----+----+
1 07 1 06 1 05 1 04 1 03 1 02 ! Dl ! DO!
07 =
MSB,
00 =
LSB
+----+----+----+----+----+----+----+----+
" ! ! ! ! !
1
1~
!
1
+-- Don't care
1 ! !
+-------
Don't care
! 1
+-------~----
Don't care
1
+-----------------
Don't care
+----------------------
Don't care
+-----~---------------------
Don't care
+--------------------------------
Don't care
+-------------------------------------
INTRQ* 0=active, l=inactive
Port Write :
The low two bits 00 and Olof this port control which drive is
se1ected.
Dl 00
o
o
1
1
o
l
o
l
Disk drive 0 selected
Disk drive 1 selected
Disk drive 2 selected
Disk drive 3 se1ected
12