MC81F4x16
8. ROM OPTION
The ROM Option is a start-condition byte of the chip. The default ROM Option value is 00H (LVR
enable and External RC is selected). It can be changed by appropriate writing tools such as
PGMPlusUSB, ISP, etc.
8.1 Rom Option
7
6
5
4
3
2
1
0
LVREN
LVRS
–
–
OSCS
ROM
OPTION
0: Enable (R35)
LVREN
LVR Enable/Disable bit
1: Disable (RESETB)
00: 2.4V
01: 2.7V
LVRS
LVR Level Selection bits
10: 3.0V
11: 4.0V
–
bit4 – bit3
Not used MC81F4x16
000: External RC
001: Internal RC; 4MHz
010: Internal RC; 2MHz
011: Internal RC; 1MHz
100: Internal RC; 8MHz
101: Not available ( Note 4 )
110: Not available ( Note 5 )
OSCS
Oscillator Selection bits
111: Crystal/ceramic oscillator
Note :
1. When LVR is enabled, LVR level should be set to appropriate value, not default value.
2. When you select the Crystal/ceramic oscillator, R33 and R34 pins are automatically
selected for XIN and XOUT mode.
3. When you select the external RC, R34 pin is automatically selected for XIN mode.
4. If OSCS is set by „101‟, Oscillator works as „Internal RC; 4MHz‟ mode.
5. If OSCS is set by „110‟, Oscillator works as „Internal RC; 2MHz‟ mode.
October 19, 2009 Ver.1.35
51
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