Section 7 Bus State Controller (BSC)
Rev. 2.00 Mar 09, 2006 page 320 of 906
REJ09B0292-0200
7.5.9
Overlap Between Auto Precharge Cycle (Tap) and Next Access
If the CPU and DMAC or E-DMAC are accessed sequentially and the first access is to SDRAM
and also in the auto precharge mode, the auto precharge cycle (Tap) of the first access may overlap
the second access if the second access is to a different memory space or to a different bank of the
same SDRAM. (Even if the second access is to the normal space, there may be an overlap with the
Tap cycle.) For this reason, it appears for the number of cycles of the second access as if access
takes place sooner (by the number of Tap cycles) than it actually does. Specific cases in which an
overlap occurs are listed in table 7.7. Also, figure 7.35 shows is a conceptual diagram of an
overlap that occurs when memory spaces CS2 and CS3 are connected to SDRAM (table 7.7, No.
3).
Table 7.7
Cases of Overlap Between Tap Cycle and Next Access
No.
First Access
Second Access
1
Space CS3, auto precharge Access to different space among CS0, CS1, CS2, and CS3
2
mode
Access to different bank in CS3
3
Space CS2, auto precharge Access to different space among CS0, CS1, CS2, and CS3
4
mode
Access to different bank in CS2
First access
to CS2 space
Tr
Tc
Td1
Td2
Td4
Tde
Tap
Tap
Td3
Tr
Tc
Td1
Td2
Overlap
Second
access to
CS3 space
Figure 7.35 Conceptual Diagram of Overlap (Conditions: SDRAM Connected to CS2 Space
(
RAS
RAS
RAS
RAS
Precharge Time Set to 2 Cycles) and SDRAM Connected to CS3 Space)
Summary of Contents for SH7616
Page 10: ...Rev 2 00 Mar 09 2006 page x of xxvi ...
Page 132: ...Section 2 CPU Rev 2 00 Mar 09 2006 page 106 of 906 REJ09B0292 0200 ...
Page 568: ...Section 12 16 Bit Free Running Timer FRT Rev 2 00 Mar 09 2006 page 542 of 906 REJ09B0292 0200 ...
Page 582: ...Section 13 Watchdog Timer WDT Rev 2 00 Mar 09 2006 page 556 of 906 REJ09B0292 0200 ...
Page 706: ...Section 16 Serial I O SIO Rev 2 00 Mar 09 2006 page 680 of 906 REJ09B0292 0200 ...
Page 820: ...Section 19 Pin Function Controller PFC Rev 2 00 Mar 09 2006 page 794 of 906 REJ09B0292 0200 ...
Page 932: ...Appendix D Package Dimensions Rev 2 00 Mar 09 2006 page 906 of 906 REJ09B0292 0200 ...
Page 935: ...SH7616 Hardware Manual ...