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Refresh Control
Unit Operation
Set "E" Bit
Load Counter
From Refresh Clock
Interval Register
Counter = ?
Decrement
Counter
Generated BIU
Request
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.
REFRESH CONTROL UNIT
BIU Refresh
Bus Operation
Refresh Request
Acknowledged
Execute
Memory Read
Increment
Address
Remove
Executed
Request
Every
Clock
Continue
A1265-0A
7-3
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