DP83936AVF datasheet(73/104 Pages) NSC

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70 Bus Interface (Continued)

A software reset immediately terminates DMA operations

and future interrupts The chip is put into an idle state where

registers can be accessed but the SONIC-T will not be ac-

tive in any other way The registers are affected by a soft-

ware reset as shown in Table 7-3 (only the Command Reg-

ister is changed)

80 Network Interfacing

The SONIC-T contains an on-chip ENDEC that performs the

network interfacing between the AUI (Attachment Unit Inter-

face) and the SONIC-T’s MAC unit A pin selectable option

allows the internal ENDEC to be disabled and the

MACENDEC signals to be supplied to the user for connec-

tion to an external ENDEC If the EXT pin is tied to ground

(EXTe0) the internal ENDEC is selected and if EXT is tied

to VCC (EXTe1) the external ENDEC option is selected

Internal ENDEC

When the internal ENDEC is used

(EXTe0) the interface signals between the ENDEC and

MAC unit are internally connected While these signals are

used internally by the SONIC-T they are also provided as an

output to the user

(Figure 8-1)

The internal ENDEC allows for a 2-chip solution for the

complete Ethernet interface

Figure 8-2 shows a typical dia-

gram of the Thin Ethernet and AUI network interface

TLF12597 – 51

FIGURE 8-1 MAC and Internal ENDEC Interface Signals

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DP83936AVF Datasheet(PDF) 73 Page - National Semiconductor (TI)