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104
Revision 3.0
G
SuperI/O Module
(Continued)
Table 4-3 provides the bit definitions for the Standard Con-
figuration registers.
All reserved bits return 0 on reads, except where noted
otherwise. They must not be modified as such modifica-
tion may cause unpredictable results. Use read-modify-
write to prevent the values of reserved bits from being
changed during write.
Write only registers should not use read-modify-write
during updates.
Table 4-3. Standard Configuration Registers
Bit
Description
Index 07h
This register selects the current logical device. See Table 4-2 for valid numbers. All other values are reserved.
Logical Device Number (R/W)
7:0
Logical Device number.
Index 20h-2Fh
SIO configuration and ID registers. See Section 4.4.1 "SIO Control and Configuration Registers" on page 106 for register/bit details.
SIO Configuration (R/W)
Index 30h
Activate (R/W)
7:1
0
Reserved.
Logical Device Activation Control.
0:
Disable
1:
Enable
Index 60h
I/O Port Base Address Bits [15:8] Descriptor 0 (R/W)
7:0
Descriptor 0 A[15:8].
Selects I/O lower limit address bits [15:8] for I/O Descriptor 0.
Index 61h
I/O Port Base Address Bits [7:0] Descriptor 0 (R/W)
7:0
Descriptor 0 A[7:0].
Selects I/O lower limit address bits [7:0] for I/O Descriptor 0.
Index 62h
I/O Port Base Address Bits [15:8] Descriptor 1 (R/W)
7:0
Descriptor 1 A[15:8].
Selects I/O lower limit address bits [15:8] for I/O Descriptor 1.
Index 63h
I/O Port Base Address Bits [7:0] Descriptor 1 (R/W)
7:0
Descriptor 1 A[7:0].
Selects I/O lower limit address bits [7:0] for I/O Descriptor 1.
Index 70h
Interrupt Number (R/W)
7:4
3:0
Reserved.
Interrupt Number.
These bits select the interrupt number. A value of 1 selects IRQ1, a value of 2 selects IRQ2, etc. (up to
IRQ12).
Note:
IRQ0 is not a valid interrupt selection.
Index 71h
Selects the type and level of the interrupt request number selected in the previous register.
Interrupt Request Type Select (R/W)
7:2
1
Reserved.
Interrupt Level Requested.
Level of interrupt request selected in previous register.
0:
Low polarity.
1:
High polarity.
This bit must be set to 1 (high polarity), except for IRQ8#, that must be low polarity.
Interrupt Type Requested.
Type of interrupt request selected in previous register.
0:
Edge.
1:
Level.
0
Index 74h
Selects selected DMA channel for DMA 0 of the logical device (0 - the first DMA channel in case of using more than one DMA channel).
DMA Channel Select 0 (R/W)
7:3
2:0
Reserved.
DMA 0 Channel Select.
This bit field selects the DMA channel for DMA 0.
The valid choices are 0-3, where a value of 0 selects DMA channel 0, 1 selects channel 1, etc.
A value of 4 indicates that no DMA channel is active.
Values 5-7 are reserved.