3069RF-ZTAT Datasheet, PDF (198/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

Example of Program Setup Procedure: Figure 6.34 shows an example of the program setup
procedure.
Set ABWCR
Set RTCOR
Set bits CKS2 to CKS0 in RTMCSR
Set DRCRB
Set DRCRA
Wait for DRAM stabilization time
DRAM can be accessed
Figure 6.34 Example of Setup Procedure when Using DRAM Interface
6.5.13 Usage Notes
Note the following points when using the DRAM refresh function.
• Refresh cycles will not be executed when the external bus released state, software standby
mode, or a bus cycle is extended by means of wait state insertion. Refreshing must therefore
be performed by other means in these cases.
• If a refresh request is generated internally while the external bus is released, the first request is
retained and a single refresh cycle will be executed after the bus-released state is cleared.
Figure 6.35 shows the bus cycle in this case.
• When a bus cycle is extended by means of wait state insertion, the first request is retained in
the same way as when the external bus has been released.
• In the event of contention with a bus request from an external bus master when a transition is
made to software standby mode, the BACK and strobe states may be indeterminate after the
transition to software standby mode (see figure 6.36).
Rev. 5.0, 09/04, page 176 of 978