AM79C971VCW datasheet(80/265 Pages) AMD

80 / 265 page

Am79C971

configure the network port and the Am79C971 control-

ler will always defer to the software driver. When The

ASEL is set to 0, the software driver should then con-

figure the ports with PORTSEL (CSR15, bits 7-8). The

GPSI does not participate in the automatic selection

process and should be manually configured with the

PORTSEL bits. If FDEN (BCR9, bit 0) is set to 1 or

DLNKST (CSR15, bit 12) is set to 1, the Network Port

Manager will continue to select the active network port,

but the internal T-MAU will not auto-negotiate the net-

work port. Instead, if FDEN (BCR9, bit 0) is set to 1, the

internal T-MAU will come up as a full-duplex T-MAU port

if link beats are found. If DLNKST (CSR15, bit 12) is set

to 1 and the internal T-MAU is active, the T-MAU will be

in a link pass state regardless of link beat.

Note:

It is highly recommended that ASEL and

PORTSEL be used when trying to manually configure

a specific network port.

In order to manually configure the External PHY, the

recommended procedure is to force the PHY configu-

rations when Auto-Negotiation is not enabled. Set the

DANAS bit (BCR32, bit 7) to turn off the Network Port

Manager. Then write again to BCR32 with the DANAS

and XPHYANE (BCR32, bit 5) bits cleared, together

with the XPHYFD (BCR32, bit 4) and XPHYSP

(BCR32, bit 3) bits set to the desired configuration. The

Network Port Manager will send a few frames to vali-

date the configuration.

If FCON (BCR32, bit 0) is set to 1, this bit will force the

internal Network Port Manager into Fast Configuration

Mode. During this mode, the Network Port Manager will

not attempt to start Auto-Negotiation on the internal as

well as the external PHY. Instead, it will rely on link in-

tegrity tests for link pass state. This will accelerate the

automatic port selection on the Am79C971 controller.

The Network Port Manager in Fast Configuration Mode

will start with the external PHY if one is detected. If the

link does not come up, the Network Port Manager will

enable the internal 10BASE-T MAU. If the internal port

also does not come up, the Network Port Manager will

continue to search the MII and the internal T-MAU ports

while enabling the internal AUI por t. The FCON

(BCR32, bit 0) should only be used if the network is ex-

periencing difficulty and is not stable.

CAUTION: The Network Port Manager utilizes the

PHYADD (BCR33, bits 9-5) to communicate with the

external PHY during the automatic port selection pro-

cess. The PHYADD is copied into a shadow register

after the Am79C971 controller has read the configura-

tion information from the EEPROM. Extreme care must

be exercised by the host software not to access BCR33

during this time. A read of PVALID (BCR19, bit 15) be-

fore accessing BCR33 will guarantee that the PHYADD

has been shadowed.

Am79C972’s Automatic Network Port selection mecha-

nism falls within the following three general categories:

s External PHY Not Present

s External PHY Present but Not Auto-Negotiable

s External PHY Present and Auto-Negotiable

Automatic Network Selection: External PHY Not

Present

The first case occurs when the MIIPD (BCR32, bit 14)

bit is 0. This indicates that there is no external PHY at-

tached to Am79C971 controller’s MII. The Am79C971

controller’s Network Port Manager will start the internal

Auto-Negotiation 10BASE-T MAU. If the Auto-Negotia-

tion 10BASE-T MAU fails to respond within a specific

time frame, then the Am79C971 controller will enable

the AUI. Auto-Negotiation FAST Link Pulses are still

being sent and the Auto-Negotiation 10BASE-T MAU is

still running. At that point, the active link can switch

back to the 10BASE-T MAU when Link Pulses or FAST

Link Pulses are detected. The only way to disable the

Auto-Negotiation process without using FDEN or

DLNKST is to enable the DANAS (BCR32, bit 7) bit or

to write to the internal/external PHYs MII control regis-

ter and disable Auto-Negotiation when the internal Net-

work Port Manager is disabled.

Automatic Network Selection: External PHY

Present but Not Auto-Negotiable

The second case occurs when the MIIPD (BCR32, bit

14) bit is 1. This indicates that there is an external PHY

attached to Am79C971 controller’s MII. If more than

one external PHY is attached to the MII Management

Interface, then the DANAS (BCR32, bit 7) bit must be

set to 1 and then all configuration control should revert

to software. The Am79C971 controller will read the reg-

ister of the external PHY to determine its status and

network capabilities. See Appendix E, Auto Negotiation

Registers, for the bit descriptions of the MII Status reg-

ister. If the external PHY is not Auto-Negotiation capa-

ble and/or the XPHYANE (BCR32, bit 5) bit is set to 0,

then the Network Port Manager will match up the exter-

nal PHY capabilities with the XPHYFD (BCR 32, bit 4)

and the XPHYSP (BCR32, bit 3) bits programmed from

the EEPROM. The Am79C971 controller will then pro-

gram the external PHY with those values. A new read

of the external PHYs MII Status register will be made to

see if the link is up. If the link does not come up as pro-

grammed after a specific time, the Am79C971 control-

ler will fail the external PHY link and start the internal

PHY process as described above. The Am79C971

controller will only start the external PHY link if the in-

ternal link has failed. If both links have failed, the AUI is

enabled but the Network Port Manager will still query

the internal and external PHYs for active links.

Automatic Network Selection: External PHY

Present and Auto-Negotiable

The third case occurs when the MIIPD (BCR32, bit 14)

bit is 1. This indicates that there is an external PHY at-

tached to Am79C971 controller’s MII. If more than one

AM79C971VCW 数据表(PDF) 80 Page - Advanced Micro Devices

AM79C971VCW 数据表(HTML) 80 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

数据表下载