Texas Instruments PCI7621, PCI7411 CardBus Memory Limit Registers 0, CardBus I/O Base Registers 0

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 PCI7x21/PCI7x11 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 PCI7x21/PCI7x11 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:		Memory limit registers 0, 1
	Offset:		20h, 28h
	Type:		Read-only, Read/Write
	Default:		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 PCI7x21/PCI7x11 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 4.31). 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:		I/O base registers 0, 1
	Offset:		2Ch, 34h
	Type:		Read-only, Read/Write
	Default:		0000 000Xh

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