TMP86FS49AIUG datasheet(44/296 Pages) TOSHIBA

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Page 28

2. Operational Description

2.2 System Clock Controller

TMP86FS49AIUG

2.2.4.4

SLOW mode

SLOW mode is controlled by the system control register 2 (SYSCR2).

The following is the methods to switch the mode with the warm-up counter.

(1)

Switching from NORMAL2 mode to SLOW1 mode

First, set SYSCR2<SYSCK> to switch the main system clock to the low-frequency clock for

SLOW2 mode. Next, clear SYSCR2<XEN> to turn off high-frequency oscillation.

Note: The high-frequency clock can be continued oscillation in order to return to NORMAL2 mode from

SLOW mode quickly. Always turn off oscillation of high-frequency clock when switching from

SLOW mode to stop mode.

Example 1 :Switching from NORMAL2 mode to SLOW1 mode.

SET

(SYSCR2). 5

; SYSCR2<SYSCK>

← 1

(Switches the main system clock to the low-frequency

clock for SLOW2)

CLR

(SYSCR2). 7

; SYSCR2<XEN>

← 0

(Turns off high-frequency oscillation)

Example 2 :Switching to the SLOW1 mode after low-frequency clock has stabilized.

SET

(SYSCR2). 6

; SYSCR2<XTEN>

← 1

(TC5CR), 43H

; Sets mode for TC6, 5 (16-bit mode, fs for source)

(TC6CR), 05H

; Sets warming-up counter mode

LDW

(TTREG5), 8000H

; Sets warm-up time (Depend on oscillator accompanied)

; IMF

← 0

SET

(EIRE). 2

; Enables INTTC6

; IMF

← 1

SET

(TC6CR). 3

; Starts TC6, 5

PINTTC6:

CLR

(TC6CR). 3

; Stops TC6, 5

SET

(SYSCR2). 5

; SYSCR2<SYSCK>

← 1

(Switches the main system clock to the low-frequency clock)

CLR

(SYSCR2). 7

; SYSCR2<XEN>

← 0

(Turns off high-frequency oscillation)

RETI

VINTTC6:

PINTTC6

; INTTC6 vector table

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