Table 7-4 Area 3 Settings, DRAM Access Cycles, and Refresh Cycles
Area 3 Settings
Read/Write Cycle by CPU or DMAC
Refresh Cycle
2-state-access area
• 3 states
• 3 states
(AST3 = 0)
• Wait states cannot be inserted
• Wait states cannot be inserted
3-state-access area
• 3 states
• 3 states
(AST3 = 1)
• Wait states can be inserted
• Wait states can be inserted
To insert refresh cycles, set the RCYCE bit to 1 in RFSHCR. Figure 7-3 shows the state
transitions for execution of refresh cycles.
When the first refresh request occurs after exit from the reset state or standby mode, the refresh
controller does not execute a refresh cycle, but goes into the refresh request pending state. Note
this point when using a DRAM that requires a refresh cycle for initialization.
When a refresh request occurs in the refresh request pending state, the refresh controller acquires
the bus right, then executes a refresh cycle. If another refresh request occurs during execution of
the refresh cycle, it is ignored.
Figure 7-3 State Transitions for Refresh Cycle Execution
Refresh
request
*
Refresh
request
*
Exit from reset or standby mode
Refresh request pending state
Requesting bus right
Executing refresh cycle
Refresh request
Refresh request
Bus granted
End of refresh
cycle
Note:
A refresh request is ignored if it occurs while the refresh controller is requesting the
bus right or executing a refresh cycle.
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