ACC2087 View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

ACC2087

ENHANCED SUPER CHIP

Unspecified 

ACC MicroTM

2087

For local bus devices operating with a fast speed CPU clock, the ACC2087 offers an option to delay the ADS#

one cycle internally to detect the local bus acknowledge or delay the AT bus for one cycle as shown below.

Register 1Ah, bit 7, programs the ACC2087 internal ADS# timing. Register 18h, bit 6, programs the AT bus

cycle delay.

Local Bus Delay Option

2.8 Intel System Management Mode Interface (SMM)

System Management Mode (SMM) is designed to handle power management interrupts that are totally

transparent to the existing programs, operating systems and CPU operation modes. The ACC2087 contains

dedicated logic to interface with SMM implemented by the Intel SL-enhanced 486 for battery-powered portable

computers. The ACC2087 utilizes the DRAMs located between segments A000h and B000h as the separate

SMM memory (SMRAM) required by SMM functions.

Before activating the SMM function, the system BIOS first needs to load the SMM service routine into the

separate SMM memory (SMRAM). During power-up, the system BIOS can turn on the ACC2087 remap

feature so that memory physically located between segment A000h to segment B000h can be accessed logically

through locations between X + 128K and X if X memory is installed in the system. The system BIOS then

loads the SMM code into this area, disables the remap and then enables ACC2087 SMM support. The remap

space is now reserved for SMM. Two 64K blocks are available and one can be programmed as segment 3000h

for executing the SMI handler. The remap function will not be available when SMM is used.

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