inter80386

 

CYCLE 1

 

 

HOLD

 

CYCLE 2

 

NON-PIPELINED

 

ACKNOWLEDGE

NON-PIPELINED

 

(READ)

 

 

 

 

(WRITE)

T1

T2

T2

Th

Th

T1

T2

CLK2[

(82384 ClK) [

HOLD [

HLDA [

BEO#-BE3#, A2-A31, [

M/IO#, D/C#, W/R#

ADS# [

NOTE: IF ASSERTING BS 16#

REQUIRES A SECOND BUS

CYCLE TO BE PERFORMED,

THE SECOND CYCLE IS

PERFORMED BEFORE

HOLD ACKNOWLEDGE

VALID 2

OUT

231630-30

NOTE:

HOLD is a synchronous input and can be asserted at any CLK2 edge, provided setup and hold (t23 and t24) require- ments are met. This waveform is useful for determining Hold Acknowledge latency.

Figure 5-26. Requesting Hold from Active Bus (NA # negated)

Provided the RESET falling edge meets setup and hold times t25 and t26, the internal processor clock phase is defined at that time, as illustrated by Figure 5-28 and Figure 7-7.

An 80386 self-test may be requested at the time RE- SET is negated by having the BUSY # input at a LOW level, as shown in Figure 5-28. The self-test requires (220) + approximately 60 CLK2 periods to complete. The self-test duration is not affected by the test results. Even if the self-test indicates a prob- lem, the 80386 attempts to proceed with the reset sequence afterwards.

After the RESET falling edge (and after the self-test if it was requested) the 80386 performs an internal initialization sequence for approximately 350 to 450 CLK2 periods. Also during the initialization, between the 20th CLK2 period and the first bus cycle, the ERROR # input is sampled to determine the pres- ence of an 80387 coprocessor versus the presence of an 80287 (or no coprocessor). To distinguish be- tween an 80287 being present and no coprocessor being present requires a software test.

90

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Image 151
Intel 80386 manual Requesting Hold from Active Bus NA # negated