Normal Floppy Mode
Normal mode. Register 3F3 contains only bits 0 and 1. When this register is read, bits 2-7 are a
high impedance.
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
REG 3F3 Tri-state Tri-state Tri-state Tri-state Tri-state Tri-state tape sel1 tape sel0
Enhanced Floppy Mode 2 (OS2)
Register 3F3 for Enhanced Floppy Mode 2 operation.
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
REG 3F3
Media
ID1
Media
ID0
Drive Type ID
Floppy Boot Drive
tape sel1 tape sel0
For this mode, MEDIA_ID[1:0] pins are gated
into bits 6 and 7 of the 3F3 register. These two
bits are not affected by a hard or soft reset.
Note: L0-CRF1-B5
=
Logical Device 0,
Configuration Register F1, Bit 5
BITS 3 and 2 Floppy Boot Drive - These bits
reflect the value of L0-CRF1. Bit 3 = L0-CRF1-
B7. Bit 2 = L0-CRF1-B6.
BIT 7 MEDIA ID 1 READ ONLY (Pin 19) (See
Table 7)
BIT 6 MEDIA ID 0 READ ONLY (Pin 20) (See
Table 8)
Bits
1
and
0
-
Tape Drive Select
(READ/WRITE). Same as in Normal and
Enhanced Floppy Mode 1.
BITS 5 and 4 Drive Type ID - These bits reflect
two of the bits of L0-CRF1. Which two bits
these are depends on the last drive selected in
the Digital Output Register (3F2). (See Table 9)
Table 7 - Media ID1
Table 8 - Media ID0
Input
MEDIA ID1
Input
MEDIA ID0
BIT 7
BIT 6
Pin 19
L0-CRF1-B5 L0-CRF1-B5
Pin 20
CRF1-B4
CRF1-B4
= 1
= 0
= 1
= 0
0
1
0
1
0
1
0
1
1
0
1
0
19
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