CHAPTER 7 CLOCK GENERATOR (
µ
PD789860 SUBSERIES)
User’s Manual U14826EJ5V0UD
70
7.3 Clock Generator Control Register
The clock generator is controlled by the following register:
•
Processor clock control register (PCC)
(1) Processor clock control register (PCC)
PCC selects the CPU clock and the division ratio.
PCC is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets PCC to 02H.
Figure 7-2. Format of Processor Clock Control Register
CPU clock (f
CPU
) selection
PCC0
0
1
f
X
f
X
/2
2
0
0
0
0
0
0
PCC0
0
PCC
7
6
5
4
Symbol
Address
After reset
R/W
FFFBH
02H
R/W
3
2
1
0
Minimum instruction execution time: 2/f
CPU
At f
X
= 5.0 MHz operation
0.4 s
1.6 s
µ
µ
Caution Be sure to clear bits 0 and 2 to 7 to 0.
Remark
f
X
: System clock oscillation frequency