PCI6515 Datasheet, PDF (70/148 Pages) Texas Instruments – SINGLE SOCKET CARDBUS CONTROLLER WITH DEDICATED SMART CARD SOCKET

4.20 CardBus Memory Limit Registers 0, 1
These registers indicate the upper address of a PCI memory address range. They are used by the PCI6515 controller
to determine when to forward a memory transaction to the CardBus bus, and likewise, when to forward a CardBus
cycle to PCI. Bits 31−12 of these registers are read/write and allow the memory base to be located anywhere in the
32-bit PCI memory space on 4-Kbyte boundaries. Bits 11−0 are read-only and always return 0s. Writes to these bits
have no effect. Bits 8 and 9 of the bridge control register (PCI offset 3Eh, see Section 4.25) specify whether memory
windows 0 and 1 are prefetchable or nonprefetchable. The memory base register or the memory limit register must
be nonzero in order for the PCI6515 controller to claim any memory transactions through CardBus memory windows
(i.e., these windows by default are not enabled to pass the first 4 Kbytes of memory to CardBus).
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Name
Memory limit registers 0, 1
Type
RW RW RW RW RW RW RW RW RW RW RW RW RW RW RW RW
Default 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bit
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Name
Memory limit registers 0, 1
Type
RW RW RW RW R
R
R
R
R
R
R
R
R
R
R
R
Default 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Register:
Offset:
Type:
Default:
Memory limit registers 0, 1
20h, 28h
Read-only, Read/Write
0000 0000h
4.21 CardBus I/O Base Registers 0, 1
These registers indicate the lower address of a PCI I/O address range. They are used by the PCI6515 controller to
determine when to forward an I/O transaction to the CardBus bus, and likewise, when to forward a CardBus cycle
to the PCI bus. The lower 16 bits of this register locate the bottom of the I/O window within a 64-Kbyte page. The upper
16 bits (31−16) are all 0s, which locates this 64-Kbyte page in the first page of the 32-bit PCI I/O address space. Bits
31−2 are read/write and always return 0s forcing I/O windows to be aligned on a natural doubleword boundary in the
first 64-Kbyte page of PCI I/O address space. Bits 1−0 are read-only, returning 00 or 01 when read, depending on
the value of bit 11 (IO_BASE_SEL) in the general control register (PCI offset 86h, see Section 4.30). These I/O
windows are enabled when either the I/O base register or the I/O limit register is nonzero. The I/O windows by default
are not enabled to pass the first doubleword of I/O to CardBus.
Either the I/O base register or the I/O limit register must be nonzero to enable any I/O transactions.
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Name
I/O base registers 0, 1
Type
RW RW RW RW RW RW RW RW RW RW RW RW RW RW RW RW
Default 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bit
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Name
I/O base registers 0, 1
Type
RW RW RW RW RW RW RW RW RW RW RW RW RW RW R
R
Default 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
X
Register:
Offset:
Type:
Default:
I/O base registers 0, 1
2Ch, 34h
Read-only, Read/Write
0000 000Xh
4−12