03.01.2015 Views

80C186EC/80C188EC Microprocessor User's Manual

80C186EC/80C188EC Microprocessor User's Manual

80C186EC/80C188EC Microprocessor User's Manual

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

BUS INTERFACE UNIT<br />

3.5.5 Temporarily Exiting the HALT Bus State<br />

A DMA request, refresh request or bus hold request causes the BIU to exit the HALT bus state<br />

temporarily. This can occur only when in the Active or Idle power management mode. The BIU<br />

returns to the HALT bus state after it completes the desired bus operation. However, the BIU<br />

does not execute another bus HALT cycle (i.e., ALE and bus cycle status are not regenerated).<br />

Figures 3-26, 3-27 and 3-28 illustrate how the BIU temporarily exits and then returns to the<br />

HALT bus state.<br />

CLKOUT<br />

HOLD<br />

HLDA<br />

AD15:0<br />

AD7:0<br />

A15:8<br />

A19:16<br />

CONTROL<br />

Valid<br />

Valid<br />

A1089-0A<br />

Figure 3-26. Returning to HALT After a HOLD/HLDA Bus Exchange<br />

3-32

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!