参数资料
型号: M34518E8SP
元件分类: 微控制器/微处理器
英文描述: 4-BIT, OTPROM, 6 MHz, MICROCONTROLLER, PDIP32
封装: 8.90 X 28 MM, 1.78 MM PITCH, PLASTIC, SDIP-32
文件页数: 129/162页
文件大小: 1149K
代理商: M34518E8SP
Rev.3.01
2005.06.15
page 67 of 157
REJ03B0008-0301
4518 Group
CLOCK CONTROL
The clock control circuit consists of the following circuits.
On-chip oscillator (internal oscillator)
Ceramic resonator
RC oscillation circuit
Quartz-crystal oscillation circuit
Multi-plexer (clock selection circuit)
Frequency divider
Internal clock generating circuit
The system clock and the instruction clock are generated as the
source clock for operation by these circuits.
Figure 56 shows the structure of the clock control circuit.
The 4518 Group operates by the on-chip oscillator clock (f(RING))
which is the internal oscillator after system is released from reset.
Also, the ceramic resonator, the RC oscillation or quartz-crystal os-
cillator can be used for the main clock (f(XIN)) of the 4518 Group.
The CMCK instruction, CRCK instruction or CYCK instruction is ex-
ecuted to select the ceramic resonator, RC oscillator or
quartz-crystal oscillator respectively.
Fig. 56 Clock control circuit structure
MR3, MR2
00
01
10
11
CMCK instruction
QS
R
Internal reset signal
Key-on wakeup signal
EPOF instruction
POF instruction
+
QS
R
0
MR0
1
Division circuit
System clock (STCK)
Instruction clock
(INSTCK)
Multi-
plexer
Quartz-crystal
oscillation
On-chip oscillator
(internal oscillator)
XOUT
XIN
Ceramic
resonance
RC oscillation
Internal clock
generating circuit
(divided by 3)
RG0
MR1
QS
R
QS
R
Q
S
R
CRCK instruction
CYCK instruction
Divided by 2
Divided by 4
Divided by 8
The CMCK, CRCK, and CYCK instructions can be used only to se-
lect main clock (f(XIN)). In this time, the start of oscillation and the
switch of system clock are not performed.
The oscillation start/stop of main clock f(XIN) is controlled by bit 1
of register MR. The system clock is selected by bit 0 of register
MR. The oscillation start/stop of on-chip oscillator is controlled by
register RG.
The oscillation circuit by the CMCK, CRCK or CYCK instruction
can be selected only at once.
The oscillation circuit corresponding to the first executed one of
these instructions is valid.
Execute the main clock (f(XIN)) selection instruction (CMCK, CRCK
or CYCK instruction) in the initial setting routine of program (ex-
ecuting it in address 0 in page 0 is recommended).
When the CMCK, CRCK, and CYCK instructions are never ex-
ecuted, main clock (f(XIN)) cannot be used and system can be
operated only by on-chip oscillator.
The no operated clock source (f(RING)) or (f(XIN)) cannot be used
for the system clock. Also, the clock source (f(RING) or f(XIN)) se-
lected for the system clock cannot be stopped.
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