uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
CHAPTER 5 CLOCK GENERATOR<br />
(2) Suboscillation mode register (SCKM)<br />
SCKM selects a the feedback resistor for the subsystem clock, and controls the oscillation of the clock.<br />
SCKM is set with a 1-bit or 8-bit memory manipulation instruction.<br />
RESET input clears SCKM to 00H.<br />
Caution <strong>Bit</strong> 2 to 7 must be set to 0.<br />
Figure 5-3. Suboscillation Mode Register Format<br />
Symbol 7 6 5 4 3 2 1 0 Address After reset R/W<br />
SCKM<br />
(3) Subclock control register (CSS)<br />
CSS specifies whether the main system or subsystem clock oscillator is to be selected. It also specifies the<br />
CPU clock operation status.<br />
CSS is set with a 1-bit or 8-bit memory manipulation instruction.<br />
RESET input clears CSS to 00H.<br />
Symbol<br />
CSS<br />
0 0 0 0 0 0 FRC SCC<br />
FRC<br />
0<br />
1<br />
SCC<br />
0<br />
1<br />
On-chip feedback resistor used<br />
On-chip feedback resistor not used<br />
Operation enabled<br />
Operation stopped<br />
Note <strong>Bit</strong> 5 read only.<br />
Figure 5-4. Subclock Control Register Format<br />
7 6 5 4 3 2 1 0<br />
0 0 CLS CSS0 0 0 0 0<br />
CLS<br />
0<br />
1<br />
CSS0<br />
0<br />
1<br />
Caution <strong>Bit</strong>s 0 to 3, 6, and 7 must be set to 0.<br />
Feedback resistor selection<br />
FFF0H 00H R/W<br />
Control of subsystem clock oscillator operation<br />
CPU clock operation status<br />
Operation based on the divided main system clock output<br />
Operation based on the subsystem clock output<br />
Address After reset R/W<br />
FFF2H 00H R/W<br />
Selection of the main system or subsystem clock oscillator<br />
Divided output from the main system clock oscillator<br />
Output from the subsystem clock oscillator<br />
Preliminary User’s Manual U14938EJ1V0UM 69<br />
Note