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.
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.
REG 3F3 Reserved Reserved
Drive Type ID
Floppy Boot Drive tape sel1 tape sel0
For this mode, DRATE0 and DRATE1 pins are inputs,
and these inputs are gated into bits 6 and 7 of the 3F3
register. These two bits are not affected by a hard or soft
BIT 7 Reserved
BIT 6 Reserved
BITS 5 and 4 Drive Type ID - These Bits reflect two of
the bits of configuration register 6.
Which two bits depends on the last drive selected in the
Digital Output Register (3F2). (See Table 11)
BITS 3 and 2 Floppy Boot Drive - These bits reflect the
value of configuration register 7 bits 1, 0. Bit 3 = CR7 Bit
DB1. Bit 2 = CR7 Bit DB0.
Bits 1 and 0 - Tape Drive Select (READ/WRITE). Same
as in Normal and Enhanced Floppy Mode. 1.
Table 9 - Drive Type ID
Digital Output Register
Register 3F3 - Drive Type ID
CR6 - Bit 1
CR6 - Bit 0
CR6 - Bit 3
CR6 - Bit 2
CR6 - Bit 5
CR6 - Bit 4
CR6 - Bit 7
CR6 - Bit 6