RX610 Group
3. Operating Modes
R01UH0032EJ0120 Rev.1.20
Page 91 of 1006
Feb 20, 2013
3.2.3
System Control Register 0 (SYSCR0)
Address: 0008 0006h
b15
b14
b13
b12
b11
b10
b9
b8
Value after reset:
0
0
0
0
0
0
0
0
b7
b6
b5
b4
b3
b2
b1
b0
Value after reset:
0
0
0
0
0
0
—
—
—
—
—
—
EXBE
ROME
KEY[7:0]
0
1
Bit
Symbol
Bit Name
Description
R/W
b0
ROME
On-Chip FLASH Enable
0: The on-chip FLASH is disabled
1: The on-chip ROM is enabled
R/W
b1
EXBE
External Bus Enable
0: The external bus is disabled
1: The external bus is enabled
R/W
b7 to b2
Reserved
These bits are always read as 0. The write value should
always be 0.
R/W
b15 to b8 KEY[7:0]
SYSCR0 Key Code
5Ah: Modifying SYSCR0 is enabled
Other codes: Modifying SYSCR0 is disabled
These bits are always read as 00h.
R/W
SYSCR0 is used to enable or disable the on-chip ROM and the external bus.
ROME Bit (On-Chip FLASH Enable)
The ROME bit enables or disables the on-chip ROM (ROM, data flash).
While this bit is 1, it can be cleared to 0. While this bit is 0, it cannot be set to 1. Once the on-chip ROM is disabled by
clearing this bit to 0, the on-chip ROM can no longer be enabled with the ROME bit. A 0 should not be written to this bit
during access to the on-chip ROM.
After writing a 0 to this bit to disable the on-chip ROM, always make sure that the ROME bit has been changed to 0
before proceeding to the next processing.
EXBE Bit (External Bus Enable)
The EXBE bit enables* or disables the external bus.
Write 0 to this bit while the external bus cycle is not performed.
Be careful when disabling the external bus because the external bus and the internal bus are concurrently activated in
some cases. When the EXBE bit is changed, the bus should be accessed after the change in the EXBE bit is completed.
When the EXBE bit is changed, the I/O port setting should also be changed simultaneously. For details, see section 14,
I/O Ports.