82091AA datasheet(46/204 Pages) INTEL

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82091AA

4112 SBCFG1SERIAL PORT B CONFIGURATION REGISTER

Index Address

40h

Default Value

0RR0 0000

Attribute

ReadWrite

Size

8 bits

The SBCFG1 register enablesdisables Serial Port B selects the Serial Port B address range and selects

between IRQ3 and IRQ4 as the Serial Port B interrupt This register also selects the appropriate clock frequen-

cy for use with MIDI

NOTES

1 Through programming of this register and the SBCFG1 Register the 82091AA permits serial ports A

and B to be configured for the same interrupt assignment However software must take care in

responding to interrupts correctly

2 It is possible to enable and assign both serial ports to the same address through software In this

configuration the 82091AA disables serial port B but does not set serial port B into it’s powerdown

condition Although this is a safe configuration for the 82091AA it is not power conservative and is

not recommended

290486 – 16

NOTE

Default shown is for SWMB and SWAI hardware configuration modes For HWB and HWE modes the default is

determined by hardware strapping options as described in Section 42 Hardware Configuration

Figure 16 Serial Port B Configuration Register

82091AA Datasheet(PDF) 46 Page - Intel Corporation