802Ah - Modem I/O BASE Register 0

7

6

5

 

4

3

2

1

0

 

 

 

 

 

 

 

 

 

A7

A6

A5

 

A4

A3

0

0

0

 

 

 

 

 

 

 

 

 

0

0

0

 

0

0

0

0

0

802Ch - Modem I/O BASE Register 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

6

5

 

4

3

2

1

0

 

 

 

 

 

 

 

 

 

A15

A14

A13

 

A12

A11

A10

A9

A8

 

 

 

 

 

 

 

 

 

0

0

0

 

0

0

0

1

1

 

 

 

 

 

 

 

 

 

The Modem I/O Base registers determine the base address of the I/O range used to access function specific registers. These registers allow the function's registers to be placed anywhere in the host's I/O space. I/O Base 0 contains the low order byte (A7-A0) and I/O Base 1 contains the high order byte (A15-A8). Since the modem function requires 8 I/O locations, bits 2-0 of I/O

Base 0 are always 0. Since only A15 to A4 are decoded by the controller (64K address space), it is up to the host to resolve any conflicts with addressing above 64K.

These registers are still accessable even if the “Enable Base and Limit” bit in the MCOR is cleared (0).

89

Page 89
Image 89
SMC Networks SMC91C95 manual 802Ah Modem I/O Base Register 802Ch Modem I/O Base Register, A15 A14 A13 A12 A11 A10