Register Description
12.2.11Offset 1Ch: IOBL—I/O  Base and Limit
This register defines the base and limit, aligned to a 4 KB boundary, of the I/O area of the bridge. Accesses from PCI Express* that are within the ranges specified in this register are sent to PCI when the I/O space enable bit is set. Accesses from PCI Express* that are outside the ranges specified result in an Unsupported Request response.
Table 45.  | Offset 1Ch:  | |||
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Bits | 
  | Type  | Reset  | Description  | 
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  | I/O Limit Address Bits [15:12] (IOLA): These bits define the top address of an address  | 
15:12  | 
  | RW  | 0h  | range to determine when to forward I/O transactions from PCI Express* to PCI. These bits  | 
  | correspond to address lines[15:12] for 4 KB aligned window. Bits[11:0] are assumed to be  | |||
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  | FFFh. | 
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11:8  | 
  | RO  | 0h  | I/O Limit Addressing Capability (IOLC): Each of these bits is   | 
  | support for  | |||
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  | I/O Base Address Bits [15:12] (IOBA): These bits define the bottom address of an  | 
7:4  | 
  | RW  | 0h  | address range to determine when to forward I/O transactions from one interface to another.  | 
  | These bits correspond to address lines[15:12] for 4 KB alignment. Bits[11:0] are assumed to  | |||
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  | |
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  | be 000h. | 
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3:0  | 
  | RO  | 0h  | I/O Base Addressing Capability (IOBC): Each of these bits is   | 
  | support for   | |||
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Intel® 41210 Serial to Parallel PCI Bridge Developer’s Manual  | 83  |