tmp89fm42 TOSHIBA Semiconductor CORPORATION, tmp89fm42 Datasheet - Page 33

• Manufacturer Part Number: tmp89fm42
• Description: 8 Bit Microcontroller
• Manufacturer: TOSHIBA Semiconductor CORPORATION

RA001
2.3.3.3
A quarter of the basic clock
for the low-frequency clock
SYSCR2<SYSCK>
SYSCR1<DV9CK>
Gear clock fcgck
frequency clock (fc).
peripheral circuits, from the gear clock (fcgck) or the clock that is a quarter of the low-frequency clock
(fs). The timing generator has the following functions:
Timing generator
(1)
Immediately after reset release, the gear clock (fcgck) becomes the clock that is a quarter of the high-
Note: Don't change CGCR<FCGCKSEL> in the SLOW mode. This may stop the gear clock (fcgck) from
The timing generator is a circuit that generates system clocks to be supplied to the CPU core and the
a machine cycle counter.
1. Generation of the main system clock (fm)
2. Generation of clocks for the timer counter, the time base timer and other peripheral circuits
Configuration of timing generator
The timing generator consists of a main system clock generator, a prescaler, a 21-stage divider and
being changed.
1. Main system clock generator
clock (fs) for the main system clock (fm) to operate the CPU core.
the clock that is a quarter of the low-frequency clock (fs).
tem clock is switched. If the currently operating oscillation circuit is stopped before the main
system clock is switched, the internal condition becomes as shown in Table 2-1 and a system
clock reset occurs. For details of clock switching, refer to "2.3.6 Operation Mode Control".
Figure 2-5 Configuration of Timing Generator
This circuit selects the gear clock (fcgck) or the clock that is a quarter of the low-frequency
Clearing SYSCR2<SYSCK> to "0" selects the gear clock (fcgck). Setting it to "1" selects
It takes a certain period of time after SYSCR2<SYSCK> is changed before the main sys-
Table 2-2 Gear Clock (fcgck)
Prescaler
CGCR<FCGCKSEL>
00
01
10
11
Divider
Timer counter, time base timer and other peripheral circuits
Main system clock generator
Page 19
Multiplexer
Reserved
A
B
S
fcgck
fc / 4
fc / 2
fc
Y
Main system clock
fm
Divider
Machine cycle counter
TMP89FM42