Intel 80C188XL, 80C186XL user manual Refresh Control Unit Operation Set E Bit

Models: 80C186XL 80C188XL

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Refresh Control Unit Operation

REFRESH CONTROL UNIT

Refresh Control Unit Operation

Set "E" Bit

Load Counter

From Refresh Clock

Interval Register

Counter = ?

Decrement

Counter

Generated BIU

Request

BIU Refresh

Bus Operation

Refresh Request

Acknowledged

Execute

Memory Read

Increment

Address

Remove

Executed Request

Every

Clock

Continue

A1265-0A

Figure 7-2. Refresh Control Unit Operation Flow Chart

The nine-bit refresh clock counter does not wait until the BIU services the refresh request to con- tinue counting. This operation ensures that refresh requests occur at the correct interval. Other- wise, the time between refresh requests would be a function of varying bus activity. When the BIU services the refresh request, it clears the request and increments the refresh address.

7-3

Page 182
Image 182
Intel 80C188XL, 80C186XL user manual Refresh Control Unit Operation Set E Bit