Section 7 Bus State Controller (BSC)
Rev. 2.00 Mar 09, 2006 page 327 of 906
REJ09B0292-0200
7.6.4
Wait State Control
When the clock frequency is raised, 1 cycle may not always be sufficient for all states to end, as in
basic access. Setting bits in WCR1, WCR2 and MCR enables the state to be lengthened. Figure
7.41 shows an example of lengthening a state using settings.
The Tp cycle (which ensures a sufficient
RAS
precharge time) can be extended from 1 cycle to 2
cycles by insertion of a Tpw cycle by means of the TRP1, TRP0 bit in MCR. The number of
cycles between
RAS
assert and
CASn
assert can be extended from 1 cycle to 3 cycles by inserting
a Trw cycle by means of the RCD1, RCD0 bit in MCR. The number of cycles from
CASn
assert
to the end of access can be extended from 1 cycle to 3 cycles by setting the W31/W30 bits in
WCR1. When external wait mask bit A3WM in WCR2 is cleared to 0 and bits W31 and W30 in
WCR1 are set to a value other than 00, the external wait pin is also sampled, so the number of
cycles can be further increased. When bit A3WM in WCR2 is set to 1, external wait input is
ignored regardless of the setting of W31 and W30 in WCR1. Figure 7.42 shows the timing of wait
state control using the
WAIT
pin.
In either case, when consecutive accesses occur, the Tp cycle access overlaps the Tc2 cycle of the
previous access. In DRAM access,
BS
is not asserted, and so
RAS
,
CASn
,
RD
, etc., should be
used for
WAIT
pin control.
Содержание SH7616
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Страница 132: ...Section 2 CPU Rev 2 00 Mar 09 2006 page 106 of 906 REJ09B0292 0200 ...
Страница 568: ...Section 12 16 Bit Free Running Timer FRT Rev 2 00 Mar 09 2006 page 542 of 906 REJ09B0292 0200 ...
Страница 582: ...Section 13 Watchdog Timer WDT Rev 2 00 Mar 09 2006 page 556 of 906 REJ09B0292 0200 ...
Страница 662: ...Section 14 Serial Communication Interface with FIFO SCIF Rev 2 00 Mar 09 2006 page 636 of 906 REJ09B0292 0200 ...
Страница 706: ...Section 16 Serial I O SIO Rev 2 00 Mar 09 2006 page 680 of 906 REJ09B0292 0200 ...
Страница 820: ...Section 19 Pin Function Controller PFC Rev 2 00 Mar 09 2006 page 794 of 906 REJ09B0292 0200 ...
Страница 932: ...Appendix D Package Dimensions Rev 2 00 Mar 09 2006 page 906 of 906 REJ09B0292 0200 ...
Страница 935: ...SH7616 Hardware Manual ...