AM79C974 datasheet(131/153 Pages) AMD

131 / 153 page

131

Am79C974

Designing a Single Motherboard for AMD

PCI Family

APPENDIX F

Three devices in the AMD PCI family, the Am53C974,

the Am79C970, and the Am79C794, were designed

with very similar pin assignments so that a single mothe-

rboard design could be used for three different prod-

ucts: one with a built-in SCSI controller, one with a

built-in Ethernet controller, and one with both a SCSI

controller and an Ethernet controller. This discussion

describes some implementation details.

Pin Out Differences

The table below shows the pins that are not the same on

the three devices. All pins that are shown as NC are not

bonded to the die inside the device package. These pins

can be driven by any signal without affecting the opera-

tion of the device. Those pins that are shown in the PCI

family data sheets as RESERVED are connected to test

logic on the die. These pins are active only during stand-

alone chip testing, and therefore they may also be con-

nected to signals on the board without affecting the

operation of the device. On the other hand, pin 116

which is shown as RESERVED-DNC (for Do Not Con-

nect) must not be connected to anything on the board.

Am79C970 (Ethernet)

Am53C974 (SCSI)

Am79C974 (Combination)

Pin Numbers

Function

RESERVED

IDSEL

IDSELA

IDSEL

IDSELB

RESERVED

PWDN

SCSICLK1

SCSICLK

68, 69, 70, 71, 73,

SCSI data & parity bus

74, 75, 77, 78

64, 65, 66, 80, 81,

SCSI control lines

83, 85, 86, 87

89, 90, 92, 93, 94, 95

10Base-T lines

XTAL1

SCSICLK2

SCSICLK

XTAL2

101, 102, 104, 105, 106, 107

AUI lines

110, 111, 112, 114

EEPROM interface &

LED pins

115

SLEEP

116

RESERVED_DNC

117

INTA

118

INTB

126

REQ

REQB

127

RESERVED

REQ

REQA

123

GNT

GNTB

124

GNT

GNTA

INTx (Pins 117 and 118)

The Am79C970 and Am53C974 devices have only one

interrupt output, which is connected to pin 117. The

Am79C974, on the other hand, has two interrupt out-

puts:

INTA, which is used for SCSI interrupts, is

connected to pin 117; while

INTB, which is used for

Ethernet interrupts, is connected to pin 118. The

motherboard can connect these pins directly to dedi-

cated inputs to its interrupt controller, or it can connect

AM79C974 Datasheet(PDF) 131 Page - Advanced Micro Devices

AM79C974 Datasheet(HTML) 131 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