CS8900 데이터 시트보기 (PDF) - Cirrus Logic

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CS8900

Highly-Integrated ISA Ethernet Controller

Cirrus Logic 

CS8900

grammed. Time required for the reset calibration

is typically 10 ms. Software drivers should not

access registers internal to CS8900 during this

time.

Hardware Standby

Hardware (HW) Standby is designed for use in

systems, such as portable PC’s, that may be tem-

porarily disconnected from the 10BASE-T cable.

It allows the system to conserve power while the

LAN is not in use, and then automatically re-

store Ethernet operation once the cable is

reconnected.

In HW Standby mode, all analog and digital cir-

cuitry in the CS8900 is turned off, except for the

10BASE-T receiver which remains active to lis-

ten for link activity. If link activity is detected,

the LANLED pin is driven low, providing an in-

dication to the host that the network connection

is active. The host can then activate the CS8900

by de-asserting the SLEEP pin. During this

mode, all ISA bus accesses are ignored.

To enter HW Standby mode, the SLEEP pin

must be low and the SLEEPE bit (Register 15,

SelfCTL, Bit 9) and the HWstandbyE bit (Regis-

ter 15, SelfCTL, Bit A) must be set. When the

CS8900 enters HW Standby, all registers and cir-

cuits are reset except for the SelfCTL register.

Upon exit from HW Standby, the CS8900 per-

forms a complete reset, and then goes through

normal initialization.

Hardware Suspend

During Hardware Suspend mode, the CS8900

uses the least amount of current of the three low-

power modes. All internal circuits are turned off

and the CS8900’s core is electronically isolated

from the rest of the system. Accesses from the

ISA bus and Ethernet activity are both ignored.

HW Suspend mode is entered by driving the

SLEEP pin low and setting the SLEEPE bit

(Register 15, SelfCTL, bit 9) while the

HWstandbyE bit (Register 15, SelfCTL, bit A) is

clear. To exit from this mode, the SLEEP pin

must be driven high. Upon exit, the CS8900 per-

SLEEP

(Pin 77)

Low

CS8900 Configuration

HWstandbyE

SLEEPE

SWSuspend

(SelfCTL, Bit A) (SelfCTL, Bit 9) (SelfCTL, Bit 8)

1

1

N/A

Link Activity

Not Present

Low

1

1

N/A

Present

Low

0

1

Low to High

N/A

1

N/A

N/A

0

N/A

High

N/A

N/A

High

N/A

N/A

Low

N/A

0

Low

N/A

0

0

N/A

1

N/A

1

N/A

0

N/A

Note: Both HW Standby and HW Suspend take precedence over SW Suspend.

CS8900 Operation

HW Standby mode:

10BASE-T receiver listens for

link activity

HW Standby mode:

LANLED low

HW Suspend mode

CS8900 resets and goes

through Initialization

Not in low-power mode

SW Suspend mode

SW Suspend mode

Not in low-power mode

Table 3.8. Low-Power Mode Operation

DS150PP2

23

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