83C795 Datasheet, PDF (68/136 Pages) List of Unclassifed Manufacturers – Ethernet System Controller

HOST INTERFACE SECTION
83C795
T he recall of LAN addres s regis ters are from the
bank selected by the 4-bit E A field and are written
to regis ters at I/O locations 08H-0F H, S WH=0.
Upon R E S E T, the E A fieldpoints to Bank 6. Unless
the E E R OM load is bypass ed by jumpers (INIT =
0000), the 83C795 recalls either 8 or 16 regis ters .
When Config #6 is jumpered, only 8 registers are
recalledandthe hardware defaults are us edfor the
confi gur ati on r egi s ter s . Al l other i ni ti al
configurations res ult in 16 regis ter loads. T hes eare
done automatically. S ince E A always initializes to
Bank 6, the initial load from the E E R OM always
pulls in the LAN addres s from same location.
R efer to F igure 6-6 for a depiction of the E E R OM
regis ter logic.
BANKS OF 8 REGISTERS IN EEROM
0
1
2
3
4
GCR2
IAR RAR BIO GCR ERFAL
5
6
7
8
LAR0 LAR1 LAR2 LAR3 LAR4 LAR5 BDID CHK
9
ALWAYS TO BANK EA
A
B
C
D
E
F
RESET
DISABLE ADAPTER
LOAD DEFAULT VALUES
INTO REGISTERS
BYPASS EEROM LOAD?
YES
NO
ARE INIT JUMPERS IN
POSITION ’6’?
YES
UPON RESET, RECALL CONFIGURATION
REGISTERS FROM THE BANK ACCORDING
TO INIT JUMPERS.
(No recall from Bank 6.)
0
1
2
GCR2
IAR RAR BIO GCR ERFAL
3
4
5
LAR0 LAR1 LAR2 LAR3 LAR4 LAR5 BDID CHK
6
ALWAYS FROM BANK EA ⁷
8
(EA powers up at ’6’) ₉
A
B
C
D
E
F
NO
RETRIEVE CONFIGURATION
REGISTERS PIDL, PIDH, IAR,
RAR, BIO, GCR FROM BANK
INDEXED BY INIT JUMPERS
RETRIEVE LAN ADDRESS
REGISTERS FROM BANK
INDEXED BY EA FIELD
ENABLE ADAPTER
NO
RECALL?
YES
RETRIEVE 8 REGISTERS
FROM BANK DESIGNATED
BY EA FIELD INTO
LAN ADDRESS REGISTERS
FIGURE 6-6. EEROM REGISTER LOGIC
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