83C795 Datasheet, PDF(69/136 Page) List of Unclassifed Manufacturers

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83C795 Datasheet, PDF (69/136 Pages) List of Unclassifed Manufacturers – Ethernet System Controller

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83C795

HOST INTERFACE SECTION

6.7.2.3 Storage Operations

T he S tore operation only copies the 8 LAN address

regis ters to the E E R OM. T his does not depend

upon INIT jumper s ettings . T he s tore operation

always moves the LAN Addres s regis ters into the

bank s elected by the 4-bit E A field.

Table 6-5 defines how each bank of 8 E E R OM

locations has been allocated:

BANK

10-1F

ALLOCATION

USER PROGRAMMABLE (âSOFTâ)

CONFIGURATION

CONFIGURATION 1

CONFIGURATION 2

CONFIGURATION 3

CONFIGURATION 4

CONFIGURATION 5

PERMANENT LAN ADDRESS

CONFIGURATION 7

CONFIGURATION 8

CONFIGURATION 9

RESERVED FOR DRIVER

CONFIGURATION STORAGE

CONFIGURATION 11

CONFIGURATION 12

CONFIGURATION 13

CONFIGURATION 14

RESERVED FOR DRIVER

CONFIGURATION STORAGE

PNP DATA

TABLE 6-5. EEROM LOCATION ALLOCATION

Unlocking the E E R OM F or Write Operations

T his convoluted method is used to protect the

E E R OM from getting accidentally eras ed by

s omeone els eâs s oftware.

T he E E R OM regis ter (E E R ) looks like this :

BIT

EER WRITE

7 STO

6 RC

5 EA4

4 UNLOCK

3 EA3

2 EA2

1 EA1

0 EA0

RESET

T he s cheme requires a s equence of three writes

into the E E R OM regis ter to s tart a s tore operation.

T hefirs t two writes are requiredtos et theUNLOCK

bit and the third write executes the store.

T he 1s t write must be:

STORE=0, RECALL=0, EA4=X, UNLOCK=0,

EA[3â0] = Ch.

T he 2nd write mus t be:

STORE=0, RECALL=0, EA4=X, UNLOCK=1,

EA[3â0] = Ah.

T he 3rd write is :

STORE=1, RECALL=0, UNLOCK=0, EA[4â0] =

EEROM bank.

T hevaluefor theE A4-E A0 fieldis theE E R OMbank

you intend to store in it.

T hewritingof any other valuetotheE E R other than

the required ones in the s equence will s et the

locking mechanism back to its initial condition and

all three writes will once again be required in

s equencetounlock thewriteprotection. Intervening

I/O operations to other registers and reads of the

E E R OM regis ter donot affect theunlock s equence.

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