97
CHAPTER 6 CLOCK GENERATOR
6.6.2 Switching CPU clock
The following figure illustrates how the CPU clock switches.
Figure 6-6. Switching CPU Clock
V
DD
RESET
CPU clock
Slowest
operation
Fastest
operation
Wait (15.6 ms: at 8.38-MHz operation)
Internal reset operation
<1> The CPU is reset when the RESET pin is made low on power application. The effect of resetting is released
when the RESET pin is later made high, and the main system clock starts oscillating. At this time, the time
during which oscillation stabilizes (2
17
/f
X
) is automatically secured.
After that, the CPU starts instruction execution at the slowest speed of the main system clock (3.81
µ
s: at
8.38-MHz operation).
<2> After the time during which the V
DD
voltage rises to the level at which the CPU can operate at the highest
speed has elapsed, PCC is rewritten so that the highest speed can be selected.
Summary of Contents for mPD780973 Series
Page 2: ...2 MEMO ...
Page 66: ...66 MEMO ...
Page 98: ...98 MEMO ...
Page 138: ...138 MEMO ...
Page 164: ...164 MEMO ...
Page 182: ...182 MEMO ...
Page 204: ...204 MEMO ...
Page 244: ...244 MEMO ...
Page 262: ...262 MEMO ...
Page 278: ...278 MEMO ...
Page 290: ...290 MEMO ...