Toshiba TMP87CP24AF - Manual (Page 27)

TOSHIBA
TMP87CM24A/P24A
(3) SLOW mode
SLOW mode is controlled by the system control register 2 (SYSCR2) and the timer/counter 2 (TC2).
a. Switching from NORMAL2 mode to SLOW mode
First, set SYSCK (bit 5 in SYSCR2) to switch the main system clock to the low-frequency clock.
Next, clear XEN (bit 7 in SYSCR2) to turn off high-frequency oscillation.
When the low-frequency clock oscillation is unstable, wait until oscillation stabilizes before
performing the above operations. The timer/counter 2 (TC2) can conveniently be used to
confirm that low-frequency clock oscillation has stabilized.
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.
Examplel : Switching from NORMAL2 mode to SLOW mode.
SET (SYSCR2).5 ; SYSCK<-1
CLR (SYSCR2). 7 XEN<-0
(Switches the main system clock to the
low-frequency clock)
(turns off high-frequency oscillation)
Example2 : Switching to SLOW mode after low-frequency clock oscillation has stabilized.
LD (TC2CR), 14H ; Sets TC2 mode
(timer mode, source clock : fs)
LDW (TREG2), 8000H ; Sets warming-uptime
(according toXtal characteristics)
SET (EIRH). EF14 ; Enable INTTC2
LD (TC2CR), 34H ; Starts TC2
PINTTC2 : LD (TC2CR), 10H ; Stops TC2
SET (SYSCR2). 5 ; SYSCK<-1
CLR
RETI
(SYSCR2). 7 ; XEN<-0
VINTTC2: DW PINTTC2 ; INTTC2 vector table
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24-27 2002
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10-03