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TI486 Microprocessor - Al Kossow's Bitsavers

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Enabling SMM<br />

A.3 Enabling SMM<br />

The enabling and setup of SMM in the <strong>TI486</strong> CPU is done by setting all 4 of<br />

the SMM registers/bits to:<br />

Register/Bit<br />

SMI<br />

SM4<br />

SM_loc<br />

SM_size<br />

Locationt Value Description<br />

CCR1 bit 1 1 Enable SMI pin<br />

CCR1 bit 7 1 Make ARR4 as SMM space<br />

ARR4 bits 12-4 Start SMM region SMM base address<br />

ARR bits 3-0 ~ 4KB and ~ 16MB SMM size<br />

t See subsection 2.3.2.4 for further information on CCR1 and ARR4.<br />

Setup example<br />

SMM Location<br />

SMM Size<br />

OC8000H<br />

8KB<br />

mov<br />

ai, Oc1h<br />

out 22h, al<br />

in<br />

ah, 23h<br />

or<br />

ah, 082h<br />

mov<br />

ai, Oc1h<br />

out 22h, al<br />

out 23h, ah<br />

mov<br />

ai, Oceh<br />

out 22h, al<br />

mov<br />

ai, Och<br />

out 23h, al<br />

mov<br />

ai, Ocfh<br />

out 22h, al<br />

mov<br />

ai, 082h<br />

out 23h, al<br />

index to CCR1<br />

select CCR1 register<br />

read current CCR1 value<br />

enable SM! and SM4 region<br />

index to CCR1<br />

select CCR1 register<br />

write new value to CCR1<br />

index ARR4 SMM base address bits <br />

select<br />

set ARR4 SMM base address upper bits<br />

write value<br />

index ARR4 SMM base address bits <br />

and 4 bits for SMM size<br />

set SMM lower address bits and SMM size<br />

write value<br />

A-a<br />

Tl486 SMM Programmer's Guide

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