AM79C970A datasheet(50/219 Pages) AMD

50 / 219 page

AMD

P R E L I M I N A R Y

Am79C970A

Target Abort

The figure below shows a target abort sequence. The

target asserts

DEVSEL for one clock. It then deasserts

DEVSEL and asserts STOP on clock 4. A target can use

the target abort sequence to indicate that it cannot serv-

ice the data transfer and that it does not want the

transaction to be retried. Additionally, the PCnet-PCI II

controller cannot make any assumption about the suc-

cess of the previous data transfers in the current trans-

action. The PCnet-PCI II controller terminates the

current transfer with the deassertion of

FRAME on clock

5 and of

IRDY one clock cycle later. It finally releases the

bus on clock 6.

Since data integrity is not guaranteed, the PCnet-PCI II

controller cannot recover from a target abort event. The

PCnet-PCI II controller will reset all CSR locations to

their STOP_RESET values. The BCR and PCI

configuration registers will not be cleared. Any on-going

network transmission is terminated in an orderly se-

quence. If less than 512 bits have been transmitted onto

the network, the transmission will be terminated imme-

diately, generating a runt packet. If 512 bits or more

have been transmitted, the message will have the cur-

rent FCS inverted and appended at the next byte bound-

ary to guarantee an FCS error is detected at the

receiving station.

RTABORT (PCI Status register, bit 12) will be set to indi-

cate that the PCnet-PCI II controller has received a tar-

get abort. In addition, SINT (CSR5, bit 11) will be set to

ONE. When SINT is set,

INTA is asserted if the enable

bit SINTE (CSR5, bit 10) is set to ONE. This mechanism

can be used to inform the driver of the system error. The

host can read the PCI Status register to determine the

exact cause of the interrupt.

19436A-22

FRAME

CLK

IRDY

TRDY

DEVSEL

REQ

GNT

23456

ADDR

0000

0111

PAR

DATA

DEVSEL is sampled

STOP

Figure 19. Target Abort

AM79C970A датащи(PDF) 50 Page - Advanced Micro Devices

AM79C970A датащи(HTML) 50 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

датащи скачать

ссылки URL