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TI486 Microprocessor - Al Kossow's Bitsavers

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Functional Timing<br />

3.2.5 Halt and Shutdown Cycles<br />

Halt Indication Cycle<br />

Executing the HLT instruction causes the <strong>TI486</strong>SLC/E execution unit to cease<br />

operation. Signaling its entrance into the halt state, a halt indication cycle is<br />

performed. The halt indication cycle is identified by the state of the bus cycle<br />

definition signals (M/IO=1, D/c=o, W/R=1, LOCK=1) and an address of 2h<br />

(A23-A2=0, A1=1, B'RE=1, BLE=O). The halt indication cycle must be<br />

acknowledged by READY asserted. A halted <strong>TI486</strong>SLC/E microprocessor<br />

resumes execution when INTR (if interrupts are enabled), NMI, or RESET is<br />

asserted. Figure 3-14 illustrates a non-pipelined halt cycle.<br />

Figure 3-14.<br />

Non-Pipelined Halt Cycle<br />

CLK2<br />

I Cycle 1 I Cycle 2 I<br />

I Non-Pipelined I Non-Pipelined I<br />

I (Write) I (Halt) I<br />

I~ .I~ ~<br />

I I I<br />

I T1 T2 I T1 T2 I Ti<br />

I I I<br />

Idle<br />

Ti Ti Ti<br />

~B~~~-----~~--~--~~~~~~~~C~re~~~~<br />

MIlO, WIR untillNTR, NMI, or ~~~~~~~ RESET is asserted. I<br />

B~~~~ ~ +d1 ~<br />

--l I l : I I I. I I<br />

ADS!\ IV !'\ ~/ I : : : I<br />

I I r I I I I I<br />

NA<br />

i~!~!'"<br />

I I I I Il I I I I<br />

I I I I ! I I I I<br />

I I I Note: Halt cycle must be acknowledged I I I<br />

I I I by READY asserted. Wait states may be I I I<br />

I I I added to the cycle if desired. I I I<br />

I . I<br />

I~II~<br />

LOCK ~ vali~1 7 i ~<br />

READY<br />

015-00<br />

I<br />

Out X Out 1 X:<br />

I<br />

I<br />

Undefined<br />

I I I I I I I<br />

>-~. (Floating)+----f----1<br />

I I I I I<br />

I I I I<br />

I<br />

I<br />

I<br />

3-32<br />

Tl486SLCIE Bus Interface

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