82374EB Datasheet, PDF (80/208 Pages) Intel Corporation – SYSTEM COMPONENT (ESC)

82374EB 82374SB
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 to a 0 on 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 7 5 A7-A5 are specific to an MSC-85 implementation These bits are not used by the ESC
interrupt controllers Bits 7 5 2 should each be initialized to 0
Bit
Description
7 5 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
4 ICW OCW Select Bit 4 must be a 1 to 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 A 1 on 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
3 Reserved This bit is not used in the ESC
2 Reserved ADI ignored for the ESC
1 SNGL This bit must be programmed to a 0 to indicate that two interrupt controllers are operating in
cascade mode on the ESC
0 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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