each logical device and is selected with the
Logical Device # Register (0x07).
Logical
Registers [0x30-0xFF]
Device
Configuration/Control
The INDEX PORT is used to select a specific
logical device register. These registers are then
accessed through the DATA PORT.
Used to access the registers that are assigned
to each logical unit. This chip supports nine
logical units and has nine sets of logical device
registers. The six logical devices are Floppy,
Parallel, Serial 1, Serial 2, Keyboard Controller,
and Auxiliary_I/O. A separate set (bank) of
control and configuration registers exists for
The Logical Device registers are accessible only
when the device is in the Configuration State.
The logical register addresses are shown in the
table below.
Table 55 - Logical Device Registers
LOGICAL DEVICE
REGISTER
ADDRESS
DESCRIPTION
STATE
ActivateNote1
(0x30)
Bits[7:1] Reserved, set to zero.
C
Bit[0]
Default = 0x00
= 1Activates the logical device currently
selected through the Logical Device #
register.
= 0 Logical device currently selected is
inactive
on Vcc POR or
Reset_Drv
Logical Device Control
Logical Device Control
Memory Base Address
I/O Base Address
(0x31-0x37) Reserved - Writes are ignored, reads return
0.
C
C
C
C
(0x38-0x3f) Vendor Defined - Reserved - Writes are
ignored, reads return 0.
(0x40-0x5F) Reserved - Writes are ignored, reads return
0.
(0x60-0x6F) Registers 0x60 and 0x61 set the base
address for the device. If more than one
(see Device Base I/O
Address Table)
0x60,2,... = base address is required, the second base
addr[15:8]
address is set by registers 0x62 and 0x63.
Refer to Table 64 for the number of base
address registers used by each device.
Default = 0x00
0x61,3,... =
addr[7:0]
on Vcc POR or
Reset_Drv
Unused registers will ignore writes and return
zero when read.
131
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