82374EB datasheet(80/208 Pages) INTEL

80 / 208 page

82374EB82374SB

ICW1 starts the initialization sequence during which the following automatically occur

a The edge sense circuit is reset which means that following initialization an interrupt request (IRQ) input

must make a low-to-high transition to generate an interrupt

b The Interrupt Mask register is cleared

c IRQ7 input is assigned priority 7

d The slave mode address is set to 7

e Special Mask Mode is cleared and Status Read is set to IRR

f If IC4 was set to 0 then all functions selected by ICW4 are set to zero However ICW4 must be programmed

in the ESC implementation of this interrupt controller and IC4 must be set to a 1

ICW1 has three significant functions within the ESC interrupt controller configuration ICW4 is needed so bit 0

must be programmed to a 1 There are two interrupt controllers in the system so bit 1 SNGL must be

programmed toa0on both CNTRL-1 and CNTRL-2 to indicate a cascade configuration Bit 4 must be a 1

when programming ICW1 OCW2 and OCW3 are also addressed at the same port as ICW1 This bit indicates

that ICW1 and not OCW2 or OCW3 will be programmed during the write to this port

Bit 2 ADI and bits 75 A7-A5 are specific to an MSC-85 implementation These bits are not used by the ESC

interrupt controllers Bits 752 should each be initialized to 0

Bit

Description

Reserved

A7-A5 are MCS-85 implementation specific bits They are not needed by the ESC These

bits should be 000b when programming the ESC

ICWOCW Select

Bit 4 must bea1to select ICW1 After the fixed initialization sequence to ICW1

ICW2 ICW3 and ICW4 the controller base address is used to write to OCW2 and OCW3 Bit 4 is a 0

on writes to these registers A1on this bit at any time will force the interrupt controller to interpret the

write as an ICW1 The controller will then expect to see ICW2 ICW3 and ICW4

Reserved

This bit is not used in the ESC

Reserved

ADI ignored for the ESC

SNGL

This bit must be programmed toa0to indicate that two interrupt controllers are operating in

cascade mode on the ESC

IC4

This bit must be set to a 1 IC4 indicates that ICW4 needs to be programmed The ESC requires

that ICW4 be programmed to indicate that the controllers are operating in an 80x86 type system

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