tmp89fm42l TOSHIBA Semiconductor CORPORATION, tmp89fm42l Datasheet - Page 50

• Manufacturer Part Number: tmp89fm42l
• Description: 8 Bit Microcontroller Tlcs-870/c1 Series
• Manufacturer: TOSHIBA Semiconductor CORPORATION

2.3
System clock controller
RB000
Quarter of the low-frequency clock
Figure 2-12 Switching of the Main System Clock (fm) (Switching from fcgck to fs/4)
PINTWUC:
SYSCR2<SYSCK>
Example 1: Switching from the NORMAL2 mode to the SLOW1 mode (when fc is used as the basic clock for the high-
Example 2: Switching to the SLOW1 mode after the stable oscillation of the low-frequency clock oscillation circuit is confirmed
Gear clock (fcgck)
Main system clock
(fs/4)
SET
NOP
NOP
CLR
; #### Initialize routine ####
SET
¦
¦
LD
LD
SET
SET
¦
; #### Interrupt service routine of warm-up counter interrupts ####
SET
NOP
NOP
CLR
RETI
¦
frequency clock)
at the warm-up counter (fs=32.768kHz, warm-up time = about 100 ms)
(SYSCR2).4
(SYSCR2).6
(P0FC).2
(WUCCR), 0x02
(WUCDR), 0x33
(EIRL).4
(SYSCR2).5
(SYSCR2).4
(SYSCR2).6
When the rising edge of fcgck is
detected twice after SYSCR2<SYSCK>
is changed from 0 to 1, f is stopped
for synchronization.
Page 36
10/fs (max.)
;SYSCR2<SYSCK> = 1
;(Switches the main system clock to the basic clock for the
;low-frequency clock for the SLOW2 mode)
;Waits for 2 machine cycles
;SYSCR2<XEN> = 0
;(Turns off the high-frequency clock oscillation circuit)
;P0FC2 = 1 (Uses P02/03 as oscillators)
;WUCCR<WUCDIV> = 00 (No division)
;WUCCR<WUCSEL> = 1 (Selects fs as the source clock)
;Sets the warm-up time
;(Determines the time depending on the oscillator characteristics)
;100 ms/1.95 ms = 51.2 → round up to 0x33
;Enables INTWUC interrupts
;SYSCR2<XTEN> = 1
;(Starts the low-frequency clock oscillation and starts the warm-up
;counter)
;SYSCR2<SYSCK> = 1
;(Switches the main system clock to the low-frequency clock)
;Waits for 2 machine cycles
;SYSCR2<XEN> = 0
;(Turns off the high-frequency clock oscillation circuit)
When the rising edge of fs/4 is detected
twice after fm is stopped, fm is switched to fs.
TMP89FM42L