SH7670 Datasheet, PDF (412/1292 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7670 Series

Section 11 Power-Down Modes
11.2.6 System Control Register 2 (SYSCR2)
SYSCR2 is an 8-bit readable/writable register that enables or disables write to the on-chip RAM
(high-speed). SYSCR2 is valid only in byte access.
When the RAMWE bit is set to 1, writing to the on-chip RAM (high-speed) is enabled. When an
RAMWE bit is cleared to 0, the corresponding on-chip RAM (high-speed) area cannot be written
to. In this case, writing to the on-chip RAM (high-speed) is ignored. The initial value of an
RAMWE bit is 1.
Note that when clearing the RAMWE bit to 0 to disable the on-chip RAM, be sure to execute an
instruction to read from or write to the same arbitrary address in each page before setting the
RAMWE bit. If such an instruction is not executed, the data last written may not be written to the
on-chip RAM (high-speed). Furthermore, an instruction to access the on-chip RAM (high-speed)
should not be located immediately after the instruction to write to SYSCR2. If an on-chip RAM
(high-speed) access instruction is set, normal access is not guaranteed.
If this bit is set to 1 to enable writing to the on-chip RAM (high-speed), the SYSCR2 read
instruction must be placed immediately after the SYSCR2 write instruction. If the on-chip RAM
(high-speed) access instruction is placed immediately after the SYSCR2 write instruction, then
normal access will not be guaranteed.
Note: See section 11.4, Usage Notes, when writing data to this register.
Bit: 7
6
5
4
3
2
1
0




RAM RAM RAM RAM
WE3 WE2 WE1 WE0
Initial value: 1
1
1
1
1
1
1
1
R/W: R
R
R
R R/W R/W R/W R/W
Bit
7 to 4
3
Bit Name

RAMWE3
Initial
Value
All 1
1
R/W
R
R/W
Description
Reserved
These bits are always read as 1. The write value
should always be 1.
RAM Write Enable 3 (corresponding RAM addresses:
Page 3 in on-chip RAM (high-speed)*)
0: On-chip RAM (high-speed) write disabled
1: On-chip RAM (high-speed) write enabled
Rev. 1.00 Nov. 14, 2007 Page 386 of 1262
REJ09B0437-0100