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CS8920A

Crystal LAN ISA Plug-and-Play Ethernet Controller

Cirrus Logic 

CS8920A

As an example, to configure the CS8920A to use

a 16-Kbyte (128-Kbit) PROM mapped into host

memory at a starting address of D0000h, write

0D00h to the BootPROM Base Address register

and write 0FC0h into the BootPROM Address

Mask register. (The mask value for a 16-Kbyte

PROM is 0FC00h. See Section 4.8 for more in-

formation on determing the BootPROM Address

and Mask register values.)

3.8 Low-Power Modes

For power-sensitive applications, the CS8920A

supports three low-power modes: Hardware

Standby, Hardware Suspend, and Software Sus-

pend. All three low-power modes are controlled

through the SelfCTL register (Register 15).

An internal reset occurs when the CS8920A

comes out of any suspend or standby mode. Af-

ter a reset (internal or external), the CS8920A

goes though a self configuration. This includes

calibrating on-chip analog circuitry, and reading

EEPROM for validity and configuration. When

the calibration is done, bit InitD in Register 16

(Self Status register) is set indicating that initiali-

zation is complete, and the SIBusy bit in the

same register is cleared (indicating that the

EEPROM is no longer being read or pro-

grammed. Time required for the reset calibration

is typically 10 ms. Software drivers should not

access registers internal to CS8920A 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 CS8920A is turned off, except for

the 10BASE-T receiver which remains active to

listen 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

CS8920A by de-asserting the SLEEP pin. Dur-

ing this mode, all ISA bus accesses are ignored.

CS8920A Configuration

SLEEP

(Pin 116)

HWstandbyE

(SelfCTL, Bit

A)

Low

Set

HWSleepE

(SelfCTL, Bit 9)

Set

SWSuspend

(SelfCTL, Bit 8)

Clear

Link Pulses

Not Present

Low

Set

Set

Low

Clear

Set

Low to High N/A

Set

Clear

Clear

Clear

Receiver

Activity

N/A

N/A

High

N/A

N/A

Clear

N/A

Low

N/A

Clear

Set

N/A

Low

N/A

Clear

Clear

N/A

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

CS8920A Operation

HW Standby mode:

10BASE-T receiver listens for

link activity

HW Standby mode:

LANLED low

HW Suspend mode

CS8920A resets and goes

through Initialization

Not in any sleep mode

SW Suspend mode

Not in any sleep mode

Table 3.8. Low-Power Mode Operation

DS238PP2

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