BANK SELECT REGISTER

 

 

 

 

 

 

 

 

 

OFFSET

 

NAME

 

 

 

TYPE

 

SYMBOL

E

 

BANK SELECT

 

READ/WRITE

 

 

BSR

 

 

 

REGISTER

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HIGH

 

0

0

 

1

1

 

0

 

0

1

 

1

BYTE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

 

1

1

0

 

0

1

1

LOW

 

 

 

 

 

 

 

 

 

BS2

BS1

 

BS0

BYTE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

X

X

X

X

 

X

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BS2, BS1, BS0 - Determine the bank presently in use.

The BANK SELECT REGISTER is always accessible except in PCMCIA powerdown mode and is used to select the register bank in use.

The upper byte always reads as 33h and can be used to help determine the I/O location of the SMC91C95.

The BANK SELECT REGISTER is always accessible regardless of the value of BS0-BS2.

The SMC91C95 implements only four banks in ISA mode, therefore, accesses to non-existing banks (BS2=1) are ignored. All six banks are accessible in PCMCIA mode.

BS2

BS1

BS0

BANK#

0

0

0

0

0

0

1

1

0

1

0

2

0

1

1

3

1

X

X

None

39

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Image 39
SMC Networks SMC91C95 manual Bank Select Register Offset Name Type Symbol READ/WRITE BSR, High Byte LOW BS2, BS0