Section 7 Bus State Controller (BSC)
Rev. 2.00 Mar 09, 2006 page 339 of 906
REJ09B0292-0200
After self-refreshing has been set, the self-refresh state continues even if the chip standby state is
entered using the chip’s standby function. The self-refresh state is also maintained even after
recovery from standby mode by means of NMI input.
In the case of a power-on reset, the bus state controller’s registers are initialized, and therefore the
self-refresh state is cleared.
Tp
Trr
CKIO
RAS
CASn
Trc1
Trc2
Trc2
Tre
Figure 7.52 DRAM Self-Refresh Cycle Timing
7.6.9
Power-On Sequence
When DRAM is used after the power is turned on, there is a requirement for a waiting period
during which accesses cannot be performed (100 µs or 200 µs minimum) followed by at least the
prescribed number of dummy
CAS
-before-
RAS
refresh cycles (usually 8). The bus state controller
(BSC) does not perform any special operations for the power-on reset, so the required power-on
sequence must be implemented by the initialization program executed after a power-on reset.
7.7
Burst ROM Interface
Set the BSTROM bit in BCR1 to set the CS0 space for connection to burst ROM. The burst ROM
interface is used to permit fast access to ROMs that have the nibble access function. Figure 7.54
shows the timing of nibble accesses to burst ROM. Set for two wait cycles. The access is basically
the same as an ordinary access, but when the first cycle ends, only the address is changed. The
CS0 signal is not negated, enabling the next access to be conducted without the T1 cycle required
for ordinary space access. From the second time on, the T1 cycle is omitted, so access is 1 cycle
faster than ordinary accesses. Currently, the nibble access can only be used on 4-address ROM.
This function can only be utilized for word or longword reads to 8-bit ROM and longword reads to
16-bit ROM. Mask ROMs have slow access speeds and require 4 instruction fetches for 8-bit
widths and 16 accesses for cache filling. Limited support of nibble access was thus added to
alleviate this problem. When connecting to an 8-bit width ROM, a maximum of 4 consecutive
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 ...