User’s Manual U13045EJ2V0UM00
96
CHAPTER 7 CLOCK GENERATOR (
µ
PD789124, 789134 SUBSERIES)
7.3 Register Controlling Clock Generator
The clock generator is controlled by the following register:
• Processor clock control register (PCC)
(1) Processor clock control register (PCC)
PCC sets the CPU clock selection and the ratio of division.
PCC is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets the PCC to 02H.
Figure 7-2. Processor Clock Control Register Format
Caution Bit 0 and bits 2 to 7 must be set to 0.
Remarks
1. f
CC
: System clock oscillation frequency
2. Values in parentheses are when operating at f
X
= 4.0 MHz.
3. Minimum instruction execution time: 2f
CPU
• When f
CPU
= 0.25
µ
s: 0.5
µ
s
• When f
CPU
= 1.0
µ
s: 2.0
µ
s
0
0
0
0
0
0
PCC1
0
PCC
Symbol
Address
After reset
R/W
FFFBH
02H
R/W
7
6
5
4
3
2
1
0
PCC1
CPU clock (f
CPU
) selection
0
1
f
CC
f
CC
/2
2
(0.25 s)
(1.0 s)
µ
µ
Содержание mPD789101
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