AM79C973VCW datasheet(93/304 Pages) AMD

93 / 304 page

Am79C973/Am79C975

P R E L I M INARY

Figure 42. EPROM Only Configuration for the Expansion Bus (>64K EPROM)

Since setting MEMEN also enables memory mapped

access to the I/O resources, attention must be given to

the PCI Memory Mapped I/O Base Address register,

before enabling access to the Expansion ROM. The

host must set the PCI Memory Mapped I/O Base Ad-

dress register to a value that prevents the Am79C973/

Am79C975 controller from claiming any memory cy-

cles not intended for it.

During the boot procedure, the system will try to find an

Expansion ROM. A PCI system assumes that an Ex-

pansion ROM is present when it reads the ROM signa-

ture 55h (byte 0) and AAh (byte 1).

Direct Flash Access

Am79C973/Am79C975 controller supports Flash as an

Expansion ROM device, as well as providing a read/

wr ite data path to the Flash. Th e Am79C9 73 /

Am79C975 controller will support up to 1 Mbyte of

Flash on the Expansion Bus. The Flash is accessed by

a read or write to the Expansion Bus Data por t

(BCR30). The user must load the upper address

EPADDRU (BCR 29, bits 3-0) and then set the FLASH

(BCR29, bit 15) bit to a 1. The Flash read/write utilizes

the PCI clock instead of the EBCLK during all ac-

cesses. EPADDRU is not needed if the Flash size is

64K or less, but still must be programmed. The user will

then load the lower 16 bits of address, EPADDRL (BCR

28, bits 15-0).

Flash/EPROM Read

A read to the Expansion Bus Data Port (BCR30) will

start a read cycle on the Expansion Bus Interface. The

Am7 9 C 9 73/ Am79C 975 con t rolle r w ill d r iv e

EBUA_EBA[7:0] with the most significant address byte

at the same time the Am79C973/Am79C975 controller

will drive AS_EBOE high to strobe the address in the

external ‘374 (D flip-flop). On the next clock, the

Am79C973/Am79C975 controller will drive EBDA[15:8]

and EBUA_EBA[7:0] with the middle and least signifi-

cant address bytes.

EBUA_EBA[7:0]

EBDA[15:8]

EBD[7:0]

EBWE

EROMCS

A[15:8]

A[7:0]

DQ[7:0]

Am79C973

EPROM

AS_EBOE

'374

D-FF

A[23:16]

21510D-47

AM79C973VCW Datasheet(PDF) 93 Page - Advanced Micro Devices

AM79C973VCW Datasheet(HTML) 93 Page - Advanced Micro Devices

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