tmp89fm46a TOSHIBA Semiconductor CORPORATION, tmp89fm46a Datasheet - Page 39

• Manufacturer Part Number: tmp89fm46a
• Description: Tlcs-870/c1 Series
• Manufacturer: TOSHIBA Semiconductor CORPORATION

2.3
System clock controller
RA000
Table 2-1 Prohibited Combinations of Oscillation Enable Register Conditions
(a) Crystal or ceramic
Don't Care
Don't Care
Don’t Care
Don’t Care
XIN
P0FC0
oscillator
0
lation, an internal factor reset is generated depending on the combination of values of the clock selected as
the main system clock, SYSCR2<OSCEN, XEN, XTEN> and the P0 port function control register P0FC0.
(1)
To prevent the dead lock of the CPU core due to the software-controlled enabling/disabling of the oscil-
Note:It takes a certain period of time after SYSCR1<OSCSEL> and SYSCR2<SYSCK> are changed before
<OSCEN>
Don’t Care
Don’t Care
Don’t Care
SYSCR2
clock (fh). When SYSCR1<OSCSEL> = "0", the internal high-frequency clock (fosc) is used as the
reference clock (fh). Upon reset release, SYSCR1<OSCSEL> is cleared to "0" and the internal high-
frequency clock (fosc) is used as the reference clock (fh).
(fc) and the internal high-frequency clock (fosc) need to be oscillating. To switch the high-frequency
reference clock (fh), be sure to follow the steps explained below.
external high-frequency clock (fc) and the internal high-frequency clock (fosc) are enabled simultane-
ously. Mode transitions, as explained in "1.3.5 Operation mode control circuit", must not be made in
this state. Once the reference clock has been switched, be sure to stop either of the high-frequency clocks
not to be used.
0
0
High-frequency clock
XOUT
the main system 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".
The high-frequency reference clock (fh) is used to operate the TMP89FM46A at high speed.
When SYSCR1<OSCSEL> = "1", the external high-frequency clock (fc) is used as the reference
When the high-frequency reference clock (fh) is switched, both the external high-frequency clock
In the process of switching the high-frequency reference clock (fh), there is a time when both the
High-frequency reference clock (fh)
Don’t Care
Don’t Care
SYSCR2
<XEN>
Figure 2-4 Examples of Oscillator Connection
0
0
1
(b) External oscillator
XIN
<OSCSEL>
Don’t Care
Don’t Care
Don’t Care
SYSCR1
0
1
XOUT
(Open)
Don’t Care
Don’t Care
Don’t Care
SYSCR2
<XTEN>
0
0
Page 20
Don’t Care
Don’t Care
<SYSCK>
SYSCR2
(c) Crystal oscillator
XTIN
1
0
0
All the oscillation circuits are stopped.
The external low-frequency clock (fs) is selected as
the main system clock, but the external low-frequency
clock oscillation circuit is stopped.
The high-frequency reference clock (fh) is selected as
the main system clock, but the internal high-frequency
clock oscillation circuit (fosc) selected as fh is stop-
ped.
The high-frequency reference clock (fh) is selected as
the main system clock, but the external high-frequen-
cy clock oscillation circuit (fc) selected as fh is stop-
ped.
The external high-frequency clock oscillation circuit
(fc) is enabled, but the relevant port pins are set as
general-purpose ports.
XTOUT
Low-frequency clock
State
(d) External oscillator
XTIN
TMP89FM46A
XTOUT
(Open)