82374EB datasheet(79/208 Pages) INTEL

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82374EB82374SB

335 CAPSCOUNTER ACCESS PORTS

040hTimer 1 Counter 0

041hTimer 1 Counter 1

042hTimer 1 Counter 2

048hTimer 2 Counter 0

04AhTimer 2 Counter 2

Default Value

xxh

Attribute

ReadWrite

Size

8 Bits per counter

Each of these IO ports is used for writing count values to the count registers reading the current count value

from the counter by either an IO read after a counter-latch command or after a read-back command and

reading the Status byte following a read-back command

Bit

Description

Counter Access

Each counter IO port address is used to program the 16 bit count register The

order of programming either LSB only MSB only or LSB then MSB is defined with the Counter

Control register at IO port address 043h The counter IO port is also used to read the current count

from the count register and return the status of the counter programming following a read-back

command

34 Interrupt Controller Registers

The ESC contains an EISA compatible interrupt controller that incorporates the functionality of two 82C59

interrupt controllers The interrupt registers control the operation of the interrupt controller and can be ac-

cessed from the EISA Bus via IO space This section describes the Interrupt registers The operation of the

Interrupt Controller is described in Chapter 90

341 ICW1INITIALIZATION COMMAND WORD 1

020hINT CNTRL-1

0A0hINT CNTRL-2

Default Value

xxh

Attribute

Write Only

Size

8 Bits per controller

A write to Initialization Command Word One starts the interrupt controller initialization sequence Addresses

020h and 0A0h are referred to as the base addresses of CNTRL-1 and CNTRL-2 respectively

An IO write to the CNTRL-1 or CNTRL-2 base address with bit 4 equal to 1 is interpreted as ICW1 For ESC-

based EISA systems three IO writes to ‘‘base address a 1’’ must follow the ICW1 The first write to ‘‘base

address a 1’’ performs ICW2 the second write performs ICW3 and the third write performs ICW4

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