SH7750_08 Datasheet, PDF (492/1162 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Section 13 Bus State Controller (BSC)
Bit 2—Refresh Control (RFSH): Specifies refresh control. Selects whether refreshing is
performed for DRAM and synchronous DRAM. When the refresh function is not used, the refresh
request cycle generation timer can be used as an interval timer.
Bit 2: RFSH
0
1
Description
Refreshing is not performed
Refreshing is performed
(Initial value)
Bit 1—Refresh Mode (RMODE): Specifies whether normal refreshing or self-refreshing is
performed when the RFSH bit is set to 1. When the RFSH bit is 1 and this bit is cleared to 0, CAS-
before-RAS refreshing or auto-refreshing is performed for DRAM and synchronous DRAM, using
the cycle set by refresh-related registers RTCNT, RTCOR, and RTCSR. If a refresh request is
issued during an external bus cycle, the refresh cycle is executed when the bus cycle ends. When
the RFSH bit is 1 and this bit is set to 1, the self-refresh state is set for DRAM and synchronous
DRAM, after waiting for the end of any currently executing external bus cycle. All refresh
requests for memory in the self-refresh state are ignored.
Bit 1: RMODE
0
1
Description
CAS-before-RAS refreshing is performed (when RFSH = 1)
Self-refreshing is performed (when RFSH = 1)
(Initial value)
Bit 0—EDO Mode (EDOMODE): Used to specify the data sampling timing for data reads when
using EDO mode DRAM interface. The setting of this bit does not affect the operation timing of
memory other than DRAM. Set this bit to 1 only when DRAM is used.
Rev.7.00 Oct. 10, 2008 Page 408 of 1074
REJ09B0366-0700