PI7C8150AND datasheet(46/111 Pages) PERICOM

46 / 111 page

PI7C8150A

2-PORT PCI-TO-PCI BRIDGE

Page 46 of 111

APRIL 2006 – Revision 1.1

4.4

VGA SUPPORT

PI7C8150A provides two modes for VGA support:

VGA mode, supporting VGA-compatible addressing

VGA snoop mode, supporting VGA palette forwarding

4.4.1

VGA MODE

When a VGA-compatible device exists downstream from PI7C8150A, set the VGA mode

bit in the bridge control register in configuration space to enable VGA mode. When

PI7C8150A is operating in VGA mode, it forwards downstream those transactions

addressing the VGA frame buffer memory and VGA I/O registers, regardless of the values

of the base and limit address registers. PI7C8150A ignores transactions initiated on the

secondary interface addressing these locations.

The VGA frame buffer consists of the following memory address range:

000A 0000h–000B FFFFh

Read transactions to frame buffer memory are treated as non-prefetchable. PI7C8150A

requests only a single data transfer from the target, and read byte enable bits are forwarded

to the target bus.

The VGA I/O addresses are in the range of 3B0h–3BBh and 3C0h–3DFh I/O. These I/O

addresses are aliases every 1KB throughout the first 64KB of I/O space. This means that

address bits <15:10> are not decoded and can be any value, while address bits [31:16] must

be all 0’s. VGA BIOS addresses starting at C0000h are not decoded in VGA mode.

4.4.2

VGA SNOOP MODE

PI7C8150A provides VGA snoop mode, allowing for VGA palette write transactions to be

forwarded downstream. This mode is used when a graphics device downstream from

PI7C8150A needs to snoop or respond to VGA palette write transactions. To enable the

mode, set the VGA snoop bit in the command register in configuration space. Note that

PI7C8150A claims VGA palette write transactions by asserting DEVSEL_L in VGA snoop

mode.

When VGA snoop bit is set, PI7C8150A forwards downstream transactions within the

3C6h, 3C8h and 3C9h I/O addresses space. Note that these addresses are also forwarded as

part of the VGA compatibility mode previously described. Again, address bits <15:10> are

not decoded, while address bits <31:16> must be equal to 0, which means that these

addresses are aliases every 1KB throughout the first 64KB of I/O space.

Note: If both the VGA mode bit and the VGA snoop bit are set, PI7C8150A behaves in the

same way as if only the VGA mode bit were set.

06-0057

PI7C8150AND Datasheet(PDF) 46 Page - Pericom Semiconductor Corporation

PI7C8150AND Datasheet(HTML) 46 Page - Pericom Semiconductor Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL