PC97338 datasheet(192/221 Pages) NSC

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TABLE 102. TRI-STATE Condition for Interrupts in Legacy Mode

Interrupt

TRI-STATE Condition

SCC1

SCC2

Parallel Port

FDC

SIRQIn

a. n = 1, 2 or 3

IRQ3,4

As described in

Section 5.

As described in

Section 5.

IRQ3 or 4 not selected

IRQ5,7

As described in

Section 4.

IRQ5 or 7 not selected

IRQ6

As described in

Section 3.

IRQ6 not selected

IRQx

b. x = 9, 10, 11, 12 or 15

IRQx

b not selected

6.2.2

Plug and Play Mode

In Plug and Play mode, software can configure the in-

terrupts of the Chip on the ISA interrupts.

It is illegal to configure two or more devices to the

same ISA interrupt, with the exception of SCC1 and

SCC2 which can be configured to the same ISA inter-

rupt.

An interrupt should be configured to a specific device

only when the device is disabled.

Tables 103 and 104 describe the possible interrupt

source for each IRQ. A plus sign (

+) means this is a

possible interrupt source and a minus sign (

−) means

it is not.

Table 104 also indicates the conditions that must be

true to enable IRQ 5, 12 and 15. All conditions in the

row (horizontally) must be true to enable the interrupt.

An x indicates the value does not matter.

Table 105 describes the conditions under which each

interrupt is put in TRI-STATE, in Plug and Play mode.

For each interrupt to be put in TRI-STATE, every col-

umn must have one true condition. If no condition is

true in any one column, the signal will not be put in

TRI-STATE.

An IRQ signal is in TRI-STATE when any of the fol-

lowing conditions is true:

• When no device is mapped to the IRQ line.

• When the device mapped to the IRQ line is inac-

tive.

• When the device mapped to the IRQ line floats its

IRQ line.

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