AM79C974 datasheet(35/153 Pages) AMD

Part #	AM79C974

Description	PCnetTM-SCSI Combination Ethernet and SCSI Controller for PCI Systems

PDF	153 Pages

Scroll/Zoom	100%

Manufacturer	AMD [Advanced Micro Devices]

Direct Link	http://www.amd.com

Logo

35 / 153 page

P R E L I M I N A R Y

AMD

Am79C974

Basic Burst Read Cycles

All Am79C974 controller burst read transfers are of the

PCI command type Memory Read Line (type14).

AD[1:0] will both be ZERO during the address phase in-

dicating a linear burst order. All four byte enable signals

will be ZERO during the data phase as the Am79C974

controller always reads a full 32-bit word when in burst

mode.

Figure 9 shows a typical burst read access. The

Am79C974 controller arbitrates for the bus, is granted

access, and reads four 32-bit words (DWORD) from

system memory and then releases the bus. All four data

phases in this example take two clock cycles each,

which is determined by the timing of

TRDY.

18681A-13

FRAME

CLK

IRDY

TRDY

DEVSEL

REQ

GNT

12345678

ADDR

0000

1110

PAR

DATA

PAR

DEVSEL is sampled by the Am79C974 controller.

Figure 9. Burst Read Cycles

AM79C974 Datasheet(PDF) 35 Page - Advanced Micro Devices