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TI486 Microprocessor - Al Kossow's Bitsavers

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Functional Timing<br />

4.2.7 Internal Cache Interface<br />

4.2.7.1 Cache Fills<br />

Any unlocked memory read cycle can be cached by the <strong>TI486</strong>DLC/E. The<br />

<strong>TI486</strong>DLC/E automatically does not cache accesses to memory addresses<br />

specified by the non-cacheable region registers. Additionally, the KEN input<br />

can be used to enable caching of memory accesses on a cycle-by-cycle basis.<br />

The <strong>TI486</strong>DLC/E acknowledges the KEN input only if the KEN enable bit is set<br />

in the CCRO configuration register.<br />

As shown in Figure 4-19 and Figure 4-20, the <strong>TI486</strong>DLC/E samples the KEN<br />

input one CLK2 before READY is sampled active. If KEN is asserted and the<br />

current address is not set as non-cacheable per the non-cacheable region<br />

registers, then the <strong>TI486</strong>DLC/E fills two bytes of a line in the cache with the<br />

data present on the data bus pins. The states of BE3-BEO are ignored if KEN<br />

is asserted for the cycle.<br />

Figure 4-18. Non-Pipelined Cache Fills Using KEN<br />

Cycle 1<br />

Non-Pipelined<br />

(Read - Cache Fill)<br />

T1 I T2 I T1<br />

$1 I $2 I 1 I 2 1 I 1 I<br />

I<br />

Cycle 2<br />

Non-Pipelined<br />

(Read - Cache Fill)<br />

T2<br />

CLK2<br />

A31-A2, BE3-BEO,<br />

Ole, MilO, wiR<br />

ADS<br />

BS16<br />

NA<br />

KEN<br />

READY<br />

LOCK<br />

031-00<br />

I I I I<br />

X X<br />

+lid1 Valid2 :<br />

I I I I I<br />

I<br />

I I I I I<br />

l\ V 1\ V<br />

~ ~<br />

I I I I<br />

I I<br />

I I<br />

I I<br />

I I I<br />

~<br />

--<br />

I I I I<br />

I I I I<br />

I I I I<br />

I I I I I<br />

~<br />

+d1<br />

~ :<br />

Valid2 :<br />

I I I I I<br />

I<br />

I<br />

-I<br />

I<br />

~<br />

I<br />

~<br />

I<br />

I<br />

•<br />

I<br />

~--r--~--r----r--~--l<br />

, I I I I , I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

I<br />

4-40<br />

Tl486DLCIE Bus Interface

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