Toshiba TMP91C824F Data Book page 23

Example 2-Setting the clock
Changing from low frequency (fs) to high frequency (fc).
SYSCR0 EQU
SYSCR1 EQU
SYSCR2 EQU
LD
SET
SET
WUP: BIT
JR
RES
RES
(note) "x" means don't care
"-" means no change
<XEN>
X1, X2 pins
<XTEN>
XT1, XT2 pins
Warming Up Timer
End of Warming Up Timer
<SYSCK>
System Clock f
SYS
00E0H
00E1H
00E2H
(SYSCR2), X−10− −X−B
7, (SYSCR0)
2, (SYSCR0)
2, (SYSCR0)
NZ, WUP
3, (SYSCR1)
6, (SYSCR0)
Counts up by f
Counts up by fc
SYS
fs
Enables Clears and Starts
High Frequency Warming Up Timer
91C824-20
14
; Sets warm-up time to 2 /fc.
; Enables high -frequency oscillation.
; Clears and starts warm-up timer.
;
Detects stopping of warm-up timer.
;
; Changes f from fs to fc.
SYS
; Disables low-frequency oscillation.
fc
Chages fsys
from fs to fc
End of warming Disables
up timer
low-frequency
TMP91C824