UPD784938 Datasheet, PDF (513/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 21 CLOCK OUTPUT FUNCTION
21.2 Clock Output Mode Register (CLOM)
The CLOM controls the clock output function.
CLOM can be read or written to with an 8-bit manipulation instruction or bit manipulation instruction.
The CLOM format is shown in Figure 21-2.
RESET input clears CLOM to 00H.
Figure 21-2. Clock Output Mode Register (CLOM) Format
7
6
CLOM LV
0
5
4
3
2
1
0 Address After reset R/W
0
CLE
0
FS2 FS1 FS0 0FFC6H
00H
R/W
FS2 FS1 FS0 Frequency Selection
0
0
0
fCLK^Note
0
0
1
fCLK/2
0
1
0
fCLK/4
0
1
1
fCLK/8
1
0
0
fCLK/16
Note Outputs the system clock
Duty ≠ 50 %
CLE
Clock Output Control
0 Outputs LV bit contents
1 Outputs clock selected by bits FS2 to FS0
LV
Output Level Control
0 Outputs low level
1 Outputs high level
Cautions 1. When the external memory expansion mode is used, the clock output mode register (CLOM) should
be set to 00H (value after RESET release).
2. The other bits (FS0 to FS2 and LV) must not be changed while the CLE bit is set (to 1).
3. The other bits (FS0 to FS2 and LV) must not be changed at the same time when the CLE bit is
changed.
Preliminary User’s Manual U13987EJ1V0UM00
513