CS8900A datasheet(28/128 Pages) CIRRUS

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DS271PP3

CS8900A

Crystal LAN™ ISA Ethernet Controller

CIRRUS LOGIC PRODUCT DATA SHEET

3.8 LED Outputs

The CS8900A provides three output pins that can

be used to control LEDs or external logic.

3.8.0.1 LANLED

LANLED goes low whenever the CS8900A trans-

mits or receives a frame, or when it detects a colli-

sion. LANLED remains low until there has been no

activity for 6 ms (i.e. each transmission, reception,

or collision produces a pulse lasting a minimum of

6 ms).

3.8.0.2 LINKLED or HC0

LINKLED or HC0 can be controlled by either the

CS8900A or the host. When controlled by the

CS8900A, LINKLED is

low whenever

the

CS8900A receives valid 10BASE-T link pulses. To

configure this pin for CS8900A control, the HC0E

bit (Register 15, SelfCTL, Bit C) must be clear.

When controlled by the host, LINKLED is low

whenever the HCB0 bit (Register 15, SelfCTL, Bit

E) is set. To configure it for host control, the HC0E

bit must be set. Table 9 summarizes this operation.

3.8.0.3 BSTATUS or HC1

BSTATUS or HC1 can be controlled by either the

CS8900A or the host. When controlled by the

CS8900A, BSTATUS is low whenever the host

reads the RxEvent register (PacketPage base +

0124h), signaling the transfer of a receive frame

across the ISA bus. To configure this pin for

CS8900A control, the HC1E bit (Register 15, Self-

CTL, Bit D) must be clear. When controlled by the

host, BSTATUS is low whenever the HCB1 bit

(Register 15, SelfCTL, Bit F) is set. To configure it

for host control, HC1E must be set. Table 10 sum-

marizes this operation.

3.8.1 LED Connection

Each LED output is capable of sinking 10 mA to

drive an LED directly through a series resistor. The

output voltage of each pin is less than 0.4 V when

the pin is low. Figure 7 shows a typical LED cir-

cuit.

3.9 Media Access Control

3.9.1 Overview

The CS8900A’s Ethernet Media Access Control

(MAC) engine is fully compliant with the IEEE

802.3 Ethernet standard (ISO/IEC 8802-3, 1993). It

handles all aspects of Ethernet frame transmission

and reception, including: collision detection, pre-

amble generation and detection, and CRC genera-

HC0E

(Bit C)

HCB0

(Bit E)

Pin Function

0N/A

Pin configured as LINKLED: Output is

low when valid 10BASE-T link pulses

are detected. Output is high if valid link

pulses are not detected

Pin configured as HC0:

Output is high

Pin configured as HC0:

Output is low

Table 9. LINKLED/HC0 Pin Operation

HC1E

(Bit D)

HCB1

(Bit F)

Pin Function

0N/A

Pin configured as BSTATUS: Output is

low when a receive frame begins trans-

fer across the ISA bus. Output is high

otherwise

Pin configured as HC1:

Output is high

Pin configured as HC1:

Output is low

Table 10. BSTATUS/HCI Pin Operation

+5V

LANLED

LINKLED

Figure 7. LED Connection Diagram

CS8900A Datasheet(PDF) 28 Page - Cirrus Logic

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