Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
6.4.3.5.3 Word Address Space Descriptor
Type 1, Large Item Name 0x8
The WORD address space descriptor is used to report resource usage in a 16-bit address space (like
memory and I/O).
Note: This descriptor is exactly the same as the DWORD descriptor specified in Table 6-196; the only
difference is that the address fields are 16 bits wide rather than 32 bits wide.
Table 6-211 WORD Address Space Descriptor Definition
Offset Field Name Definition
Byte 0 WORD Address Space Value = 0x88 (10001000B) – Type = 1, Large item name = 0x08
Descriptor
Byte 1 Length, bits [7:0] Variable length, minimum value = 0x0D (13)
Byte 2 Length, bits [15:8] Variable length, minimum value = 0x00
Byte 3 Resource Type Indicates which type of resource this descriptor describes.
Defined values are:
0 Memory range
1 I/O range
2 Bus number range
3–191 Reserved
192-255 Hardware Vendor Defined
Byte 4 General Flags
Flags that are common to all resource types:
Bits [7:4] Reserved (must be 0)
Bit [3] Max Address Fixed, _MAF:
1 The specified maximum address is fixed
0 The specified maximum address is not fixed
and can be changed
Bit [2] Min Address Fixed,_MIF:
1 The specified minimum address is fixed
0 The specified minimum address is not fixed
and can be changed
Bit [1] Decode Type, _DEC:
1 This bridge subtractively decodes this address
(top level bridges only)
0 This bridge positively decodes this address
Bit [0] Ignored
Byte 5 Type Specific Flags Flags that are specific to each resource type. The meaning of the
flags in this field depends on the value of the Resource Type field
(see above).
Byte 6 Address space granularity,
_GRA bits[7:0]
A set bit in this mask means that this bit is decoded. All bits less
significant than the most significant set bit must be set. (In other
words, the value of the full Address Space Granularity field (all 16
bits) must be a number (2 n -1).
Byte 7 Address space granularity,
_GRA bits[15:8]
360 April, 2015 Version 6.0