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DM9081

10 BASE-T hub controller

Davicom Semiconductor, Inc. 

DM9081

10BASE-T Hub Controller

External Logic

A simple logic scheme is required when more than

two DM9081 chips are connected to increase the

total number of repeater ports. The external logic

should have one input (EXPOUT#) and one output

(EXPIN#) for each DM9081 chip. This function is

easily implemented in a PAL device, using the

following logical equations:

EXPIN1# =

EXPIN2# =

EXPIN3# =

.

.

.

EXPINn# =

EXPOUT2# &

EXPOUT1# &

EXPOUT1# &

.

.

.

EXPOUT1# &

EXPOUT3# &

EXPOUT3# &

EXPOUT2# &

.

.

.

EXPOUT2# &

….. EXPOUTn#

….. EXPOUTn#

….. EXPOUTn#

.

.

.

….. EXPOUTN-1#

The above equations are in positive logic, i.e., a

variable is true when asserted. An example of three

banked DM9081 chips is shown in Figure 1. The

cascade IC number recommended: under 3 and

inclusive.

Note that if the design includes only two DM9081

chips, then EXPOUT1# is connected to EXPIN2#,

EXPOUT2# is connected to EXPIN1#, and no

external logic is required. A single PAL16L8 performs

the arbitration function for a repeater based on

several DM9081 chips.

Figure 1. Multiple DM9081 Devices

8

Final

Version: DM9081-DS-F02

February 02, 2001

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